Bug 548846: Mylyn should use High Resolution PNGs

Changes icons in org.eclipse.mylyn.tasks.ui to high resolution PNGs.
Also removes unused icons.

Wizard banner icons are mostly still low resolution. But as they have
much more pixels than the "normal" 16x16 icons this is not that
visible. As they are much more work to draw this is postponed for now.

Change-Id: Id69918426e9d1842c02b80e2a84ccaab5534acb7
Signed-off-by: Matthias Becker <ma.becker@sap.com>
217 files changed