[514079] Default to TextMergeViewer resources for icons/labels/tooltips 

- Wrap the resource bundle of an EMF Compare content merge viewer to
default to the Eclipse Compare TextMergeViewer resources for any
non-defined key to avoid re-definition problems, e.g., different values
on different platforms.

- Remove defined, identical key-value pairs for toolbar actions from the
properties of the content merge viewers.

Bug: 514079
Change-Id: I9e17bebc2ff16f830cc4812ba16acca274d773fb
Signed-off-by: Martin Fleck <mfleck@eclipsesource.com>
8 files changed