Beginning of lightweight GUI support.

- Added CMake variable to enable / disable building the lightweight GUI.
- Made some elements of the menu and toolbar hidden when in lightweight mode.
- Hid some options of the Anatomy class when in lightweight mode.
Lightgui now applied to Fibers and Fibersgroup datasets, and fibers related options.
Lightgui now applied to Glyph derived datasets.

Also moved some interface objects, to have a better layout.
Lightgui now applied to IsoSurfaces and Meshes.

Also moved some interface objects, to have a better layout.
Applied lightweight to selection objects.
Made the lightweight GUI the default one.
Fixed the size of local flipping buttons on Linux.
Merge branch 'master' into feature-lightweight
Merge branch 'master' into feature-lightweight
Merge branch 'master' into feature-lightweight
Merge branch 'master' into feature-lightweight
Hid various coloring modes for fibers.
Merge branch 'master' into feature-lightweight
Merge pull request #126 from jchoude/feature-lightweight

Create lightweight GUI version