This incorporates the last hunk of qt-creator/merge_requests/180 by Nikita V.

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

And make use of it to accept on the command line the patterns:
"filename" "+45", "filename" ":23", "filename:12" and "filename+42"

Task-Nr: QTCREATORBUG-2428

Readd a few mode switchings that I accidentally removed.

Task-Nr: QTCREATORBUG-2405

(cherry picked from commit c3649d4f)

Using more *::Constants::ICON_* where it makes sense and
wrapping the file names into QLatin1String where they were
missing.

The increased usage of the ICON constants needed a few more
cross plugin includes of *constants.h, here and there.
I think that it is OK, since the dependencies were alredy there
icon resource wise.

Move open project dialog handling into ProjectExplorer and make it
use its list of project file patterns. Same in Checkout wizards.

Task-number: QTCREATORBUG-1759
Reviewed-by: dt

 - lessens open file handles
 - improves help plugin startup further

Task-number: QTCREATORBUG-337
Reviewed-by: ck

This reverts commit 5234c775 and 21065291.

Task-number: QTCREATORBUG-1571
Reviewed-by: Leena Miettinen

To get QML functionality back, export QTCREATOR_WITH_QML before
running qmake

Reviewed-by: Kai Koehne

Reviewed-by: Leena Miettinen

Reviewed-by: Leena Miettinen

This is not only a waste of ressources, but breaks a check later on
which tries to load the QML examples from Creators ressource path
if no QML capable Qt version is found (included with Creator packages)

Reviewed-by: dt

Reviewed-by: dt

We already have it in the projects mode so we might as well
use the same in "Getting Started".

Reviewed-by: danimo

By popular request I added a "open project" option.
We don't currently have a way of differentiating project types
from other files so I had to hardcode .pro and .qmlproject
for now.

Themed icons was also added to the new and open buttons.

Reviewed-by: danimo
Task-number: QTCREATORBUG-1142

Reviewed-By: Jens Bache-Wiig

Task-number: QTCREATORBUG-1116

Remove HTML-formatting and replace by properties set in constructor.
Use in forms.

- Fix typos
- Fix layout on OS X

Done with Danimo. Most changes are cosmetic but we modified
the tutorial listing and re-arranged some of the layouts to
better reflect the suggestions by Ergosign and Nigel.

Looks more structured now.

Fixes creating these pages unnecessarily when the Welcome plugin is not
loaded, as well as "leaking" them in that case.

Reviewed-by: con

Reviewed-by: kh1

We need to append "?view=split"to force the split mode check. Make the
check more readable in viewerForContextMode.

In case of split mode we did not check if the actual requested doc
exists and thus did fail to open the browser if it could not be found.

Reviewed-by: Daniel Molkentin

Reviewed-by: ck

QString: Use QChar where appropriate.

doing it in 1.3 as well to avoid possible later conflicts

 * Tips on welcome page still explained CTRL-6 for output mode.
   Remove this.

(cherry picked from commit a8667254)

Fixes: QTCREATORBUG-483
(cherry picked from commit 8929bb27)