Merge changes from origin/7.1

Merge changes from origin/7.1

8245079 Decrease the websocket buffer size due to a Jetty 9.1 issue (#13087)
ea8f381 Show the widgetset name to more easily spot misconfigurations
797ebdf Allow user to override Atmosphere init params set by Vaadin (#13088)
65c2f2b Properly remove shadow event listeners to prevent IE8 memory leak (#13129)
e9a547a Fixed spelling mistake in log message.
0b95f8d Moved selection of selected rows in TableConnector to occur after the new rows are created (#13008)
0579fba Upload control with empty selection (#9602)
db4dba4 Ensure event listener is a widget before casting #13130
5e8e866 Changes padding for Textfields with Chameleon theme. (#12974)
171e68d Only use ClientRcp and ServerRpc types that are interfaces (#13056)
e41a2ce Add helper for adding multiple components to AbstractTestUI
407bdb3 Ignores scroll events while update from server is in progress (#11454)

Change-Id: I5d21b4071165b02da0f53bd055fb1c64e90cae5b