* fix: Add secret to all webhook's payload where it has been missing

affects webhooks for:
* Delete
* Fork
* IssueComment
* Release

* Add Attachment API
* repos/:owner/:repo/releases (add attachments)
* repos/:owner/:repo/releases/:id (add attachments)
* repos/:owner/:repo/releases/:id/attachments
* repos/:owner/:repo/releases/:id/attachments/:attachment_id

Signed-off-by: Jonas Franz <info@jonasfranz.de>

* Add unit tests for new attachment functions
Fix comments

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* fix lint

* Update vendor.json

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* remove version of sdk

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Fix unit tests
Add missing license header

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add CreateReleaseAttachment
Add EditReleaseAttachment
Add DeleteReleaseAttachment

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add filename query parameter for choosing another name for an attachment

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Fix order of imports

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Restricting updatable attachment columns

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* gofmt

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Update go-sdk
Replace Attachments with Assets

Signed-off-by: Jonas Franz <info@jonasfranz.de>

* Update go-sdk

Signed-off-by: Jonas Franz <info@jonasfranz.de>

* Updating go-sdk and regenerating swagger

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Add missing file of go-sdk

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Change origin of code.gitea.io/sdk to code.gitea.io/sdk
Update code.gitea.io/sdk

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Update swagger

Signed-off-by: Jonas Franz <info@jonasfranz.software>

* Update updateAttachment

* Update swagger documentation

Add docs for missing endpoints
Add documentation for request parameters
Make parameter naming consistent
Fix response documentation

* Restore delete comments

* Add swagger comment for adminCreateOrg

* Add swagger comment for admin route

* add hook swagger doc

* Add tags

* Add auth

* Fix name of responses

* Edit name method

* Update vendor

* make generate-swagger

From code.gitea.io/go-sdk/gitea
  To code.gitea.io/sdk/gitea

- Update import paths from github.com/go-gitea to code.gitea.io
- Fix import path for travis

See https://docs.travis-ci.com/user/languages/go#Go-Import-Path