Add GyroGuide extension

In neurosurgery, it is essential to determine the trajectory angle and
depth. Furthermore, the angle and depth have to be transmitted to the
probe for real time navigation. This extension implements these
functions. First, it calculates the entering angle and depth between the
probe and the reference planes based on CT/MRI scan. Then, the
calculated parameters can be transmitted to a gyroscope-based device
which is attached to the probe. The surgeons can be guided to operate
precisely by matching the output of gyroscope with the calculated angle,
and comparing the scale on the probe and the calculated depth.
Modify iconurl

Modify iconurl from
http://www.slicer.org/slicerWiki/index.php/File:GyroGuide.png
to
http://www.slicer.org/slicerWiki/images/a/a7/GyroGuide.png
BUG: Updating DTIProcess from r213 to r214

BUG: Searching for SVN and passing its path in the Superbuild process to compile as a Slicer extension. The value of this variable seems to be required:
http://slicer.cdash.org/viewBuildError.php?buildid=192440

http://www.nitrc.org/plugins/scmsvn/viewcvs.php?view=rev&root=dtiprocess&revision=214
Merge pull request #586 from fbudin69500/update-DTIProcess

BUG: Updating DTIProcess from r213 to r214
Update UKFTractography
ENH: Update DTIAtlasFiberAnalyzer from r128 to r130

BUG: On Windows, the extension of the executable has to be set for the tests to pass. the variable 'extension' was used instead of 'fileextension'
http://www.nitrc.org/plugins/scmsvn/viewcvs.php?view=rev&root=dti_tract_stat&revision=130

BUG: Updated version of DTIProcess that is compiled as part of DTIAtlasFiberAnalyzer and addition of CMake variables to the DTIProcess ExternalProject so that it can build as an extension
http://www.nitrc.org/plugins/scmsvn/viewcvs.php?view=rev&root=dti_tract_stat&revision=129
Merge pull request #588 from pnlbwh/update-UKFTractography

Update UKFTractography
Merge pull request #589 from fbudin69500/update-DTIAtlasFiberAnalyzer

ENH: Update DTIAtlasFiberAnalyzer from r128 to r130
added guide, loadable module, safe label setting
kslice deprecated, replaced by CarreraSlice
Merge pull request #591 from ikolesov/update-CarreraSlice

added guide, loadable module, safe label setting
Merge pull request #592 from ikolesov/update-KSlice

remove deprecated kslice, it has been replaced by CarreraSlice
Update TCIA Browser
Merge pull request #593 from mehrtash/update-TCIABrowser

Update TCIA Browser
Merge pull request #579 from lpfang/add-GyroGuide

Add GyroGuide extension
fixing mac cmake error
Merge pull request #594 from ikolesov/update-CarreraSlice

fixing mac cmake error