Support description for project plugin configuration parameter

For project plugin configuration parameter it is now possible to
provide a description. If set this description is shown as a tooltip
on an info icon that is displayed for the project plugin configuration
parameter on the ProjectInfoScreen.

The info icon is taken from the Tango Icon Library [1].

[1] http://tango.freedesktop.org/Tango_Icon_Library

Change-Id: I1f680aa24dca919ad63a6b1a8b48203734e3dfa7
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
7 files changed