SWTExceptions

Added a new SHOW_PROBLEMS_VIEW_DECORATIONS_ON_STARTUP preference,
disabled by default. Changed IDEWorkbenchPlugin to use that preference
and do not initialize hidden problems view if preference is "false".

Additionally fixed the init code to not access Display.getDefault() in
non-UI thread to avoid SWTExceptions.

Change-Id: Ife2cf2bdfce6cd6a5f3dcd51b6c2bcc7a3131119
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>