ENH: Add MarkDuplicateFramesInvalidImageFilter.

The screengrabber's frame rate is often higher that the ultrasounds's frame
rate, so detect duplicate frames (or partial duplicates with an incomplete
refresh) by subtracting subsequent frames.
ENH: Add duplicate frame detection functionality to ConvertInnerOpticToPlus.
BUG: Remove incorrect SyncRecord assert.

This is reporting 3 * 960 * 768 + 4096.  Remove hard-coded value.
Merge pull request #160 from thewtex/SyncRecord-assert

BUG: Remove incorrect SyncRecord assert.
ENH: Add command line parameter to average overlapping pixels.

This can be used to compare the results of averaging to the
blending algorithm implemented in MergeAdjacentImages.

Change-Id: Ia0567d4a687aa788c3921064101ef16fbf63d92c
Merge pull request #159 from thewtex/detect-duplicate-frames

Detect duplicate frames
COMP: Fix extension build simplifying Qt version requirement rules

See Slicer r22466 commit:

// --------------
As explained in issue #3325, on linux to prevent a crash occurring when
a page is loaded in a QWebView, at least Qt 4.8.1 is needed
on Ubuntu 13.04. Alberto also reported it is crashing when using
Ubuntu 12.04 (see #3394).

To prevent developer from having to explicitly pass
the Slicer_REQUIRED_QT_VERSION option, the requirement scheme
has been simplified.

Removed non working option "Slicer_EXPERIMENTAL_QT_VERSION" and requires
at least Qt 4.7.4 on all platform.

This revert commit r21743 and partially revert r21727

We will discuss with the community if it makes sens to required Qt >= 4.8.1
on all platform. On MacOSX, this implies that Leopard won't be supported
anymore.
// --------------
ENH: Accentuate regions based on training and given multiple input images
Merge pull request #163 from aylward/EnhanceUsingDiscriminantAnalysis

ENH: Accentuate regions based on training and given multiple input images
Merge pull request #161 from chrismullins/average-overlapping-pixels-option

ENH: Add command line parameter to average overlapping pixels.
Merge pull request #162 from jcfr/fix-qt-version-check

COMP: Fix extension build simplifying Qt version requirement rules