Updated Javadoc documentation.

Fixed erroneous initialization of editors that remained open from the
last session when Spotter Service is not online on startup. Now only a
blank page with an error message is shown.

Fixed "invalid thread access" tooltip bug.

Fixed some bugs in AddExtensionsDialog in case when Spotter Service was
offline. Additionally the dialog will not open anymore when there is no
connection.

Deleted no longer needed class SimpleExtensionsRenderer.

Change-Id: I0513330936e908d9adde8595fa07031d2e6c715f
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>
Reworked navigator viewer elements. Updated context menu, so "Open",
"Duplicate" and "Delete" are now content aware.

Added context entry "Open" for elements that can be opened in the
navigator.

Implemented possibility to delete Run Result nodes in the navigator.

Improved update process of Results. When selecting Run Result nodes the
Results View is only changed if the node actually changed.

Fixed focus bug in editors.

Change-Id: Ie64626abba21d7581d708469f29cd59eaf476744
Signed-off-by: Denis Knoepfle <denis.knoepfle@sap.com>
Merge pull request #33 from DenisKnoepfle/master

Updated Javadoc documentation of the UI / Improvement of Navigator Viewer