Add additional class names and style to components and error indicators to distinguish different error levels.

Vaadin 8 implementation of #9816. Cherry picked changes and added compatibility package component changes and tests.

Resolves #3139

* Fix Button as a Html5 DragSourcei

It was completely broken, not being clickable, and also preventing anything else from being clicked.

* Refactor Html5 DnD client side based on API review

- Moved classes to "correct" packages.
- Removed method DragSourceExtension.clearDataTransferText()
- Remove ButtonDragSource in favor of more generic API

Change-Id: I6485dee1ebba12b180a9063ed4b530f7dc63cd77

Change-Id: I4c852b7f9928e190572876690d5bef1234494a5d

Change-Id: I33f1cc33969ff74a95b1b8cc0f2add589be5aae0

Change-Id: I36c426086a2b957f6f738d17470c499a01ddac3b

Change-Id: I2e4fb3fb941fda2aa4cbc7154fa9a3f7e8e9ce02

Change-Id: I4a0e580aef1a97ce69238ea0d476599883928d84

Change-Id: Id34a8463ff40b1351d4d8b171e561a21fc76d747

Change-Id: Ic77338304dc7e58e49f27dcdaf0bab2e00f5bba6

Change-Id: I8ea2b781fab42458bf55a751c1229e391365e965

Renamed Icon to ImageIcon

Change-Id: I608815f17a3651b205fed81b5294385df0d68802

Extracted the abstract client-side Icon class

Change-Id: Ic32e270595a5796d0bbd1dd31f34282b56672aa9

Created the FontIcon class

Change-Id: Iad13871e7bf1807dee2c538c76306d4620191f5e

Renamed AbstractComponentConnector.getIcon to getIconUri

Change-Id: I6953ab79661993b561655d483c1bd013b66407f3

Added the AbstractComponentConnector.getIcon method

Change-Id: I6fb91dc643fb09da3ba53666b1a8a289901702e3

Refactored getIcon

Change-Id: Ibae39e66d0fb8449e20ac5209eb8c18b6ada4387

Made all existing uses of Icon compatible with FontIcons

Change-Id: I8f28ec5254f2e5282a887519d3f44bc1e27aba72

Initial server-side support for font icons - does not include an actual icon set yet (#13152)

Change-Id: Ie6c09b17dd577c726e0efc13567749f6f4d56d8d

Changed server side FontIcon URI generation to match the correct scheme

Change-Id: I3628b930b310b3f285bc58a3f471e31e641d307e

Initial server-side icon font (FontAwesome) with scss - to be considered placeholder for testing (#13152)

Change-Id: I361e62aba0d943a736471824e149d65c7eea9c76

Changed the FontIcon URI scheme

Change-Id: I15c92f6bb3d0aa0a800f3f0bfa80419979453e17

Added FontIcon support to AbstractOrderedLayoutConnector

Change-Id: I3b2b45b22d29622fd888dbe922aa0cc8a718104d

Added FontIcon support to table items

Change-Id: Id22ce94c96a892420aab1e39663688fc9f3bc282

Added FontIcon support to OptionGroup items

Change-Id: Ie08bef688f6802182ef5f8b2bf82cf8b1f9096bb

Switched to openly use FontAwesome (#13152)

Change-Id: I18c3325ce93915b7fd6e338c8c293a89711277bc

VaadinIcons are now FontAwesome (#13152)

Change-Id: I0ab2a80735cbf08b6e33d358e3e8c6a205626fc4

VCaption does not longer set icon to 0x0px if it's a FontIcon (#13152)

Change-Id: Ibcd96e0f79f0adf2e217a8580d17f1cc93705710

Fixed typo in @font-face, removed .otf (#13152)

Change-Id: I698ca32c560e5f198c32a6c44f7884d3030ee610

Make font icons behave more like img (display:inline-block) (#13152)

Change-Id: Ic79186c90f1fc566deae1f4d8d4ba2c21d89a42e

Change-Id: I23a26fbc5281e76792e257321d96f3d30a8bc2b2

Change-Id: I88fea408e110dc454c8d37cf0e95e109e8d8c8d1

Accessibility functions for Button

Change-Id: I12ddfd8232d4d35135add1cb4406bfdc20b758f2

Change-Id: Ia119b93643678494db95d36ffe031a44b76ba578

Change-Id: I8dbda413f2148f2a28e3867bffe0bc7ea3c8ff93

Change-Id: I419ce4581d1a8b84d4236a85a1333d23f3423b2e

This reverts commit a003c8724c

Change-Id: Ie73b6f0455a9f8ba1ed5a8cee7573ae998a67b17

Change-Id: I14f46e6aa4f9cbdd9037f1c4ad1ac38fe7cbda86

Change-Id: I5bc64ed7446ca6f87311bf63f49fb883cfd8b538

Change-Id: I52ca9908763cc7416a2c50971252429cd8c294e8

Change-Id: I0514bc4da186360a84d9cdb48140245108847115

Change-Id: I1bc200afa9f4a4f3c5e469eb0b2f93278cca97a7

@Component is not good as the server side does not have to be a Component

Class loaders have problems with referring to static inner classes (e.g.
state classes) when they cannot load the declaring class. To deal with
this the components have been moved to their own packages and state/rpc
classes will be defined in their own Java files.

Added FocusAndBlurServerRpc for sending focus and blur events to any
component.

Components that do not delegate caption handling to parent should not
get a caption

This change removes support for error messages on tabs of a tabsheet or
an accordion. Those should be implemented differently if needed.

This is an intermediate step towards moving error messages from UIDL to
shared state.

shared state and RPC calls