ids are now checked if they are a qml keyword

sci files are now supportted for BorderImage

Add XML-elements allowing for Javascript-based
validation rules along with error messages.
Rubber-stamped-by: Erik Verbruggen <erik.verbruggen@nokia.com>

Add legacy to retrieve old values.

Task-number: QTCREATORBUG-2456

In some cases snippets have a description. Due to the sorting this
already places them after keywords. So this is just to be consistent
for all cases.

Reviewed-by: Roberto Raggi

Not really visible to the user, but lead to double activation on clicking.

Task-Nr: QTCREATORBUG-1130

Reviewed-by: Roberto Raggi

Task-number: QTCREATORBUG-2454

- Move RSSFetcher to CorePlugin
- Rename RSSFetcher to RssFetcher
- Make RssFetcher more generic, allow multiple sources to be fetched
- Introduce Featured Items on Getting Started page
- Introduce dummy entry for Mobile examples, needs implementation once they are ready

Fix commiting with Author and Email set on Windows.

Task-number: QTCREATOR-2397

Update screen shot.

Reviewed-by: Lasse Holmstedt

Reviewed by: Kai Koehne

 * Handle environment variables in workdir, executable name as
   well as arguments when starting an application
 * Cover both debugger and normal application starts

Reviewed-by: dt

Expand environment variables in working directory, executable name
as well as arguments of the CustonExecutableRunConfiguration.

Reviewed-by: dt

 * Expand environment arguments
 * Introduce new kind: ExistingCommand
 * Use PATH to look up ExistingCommand

Reviewed-by: dt

Add a method to find an executable:
 * Expand environment variables
 * If relative: Check provided directories
 * If still not found: Check the path

Reviewed-by: dt