Enhancement: added node colors for every node class

In the user preferences all node classes can get its own color
The in/out color is splitted into 2 sepatate colors
the rna has been updated to better names
Enhancement: By default do not show the previews of composite nodes
only input nodes will show the preview by default.
Compositor node preview:

moved the hide preview logic to a method on bNodeTreeType. This way the node.c keeps clean, but logic could still be shared.
Implementing this per node, can lead to future errors.
PREVIEW: updated the default themes.
Refactoring/cleanup, borrowed from soc-2013-paint branch.

* Move symmetry options to the paint struct (where all paint systems can
make use of it)

* Rename draw_pressure to stroke_active. This is what is really checked
on those occasions that this is used. Also move turning on/off of this
option to the stroke level and avoid doing it on every stroke system.

* Rename BRUSH_RESTORE_MESH to BRUSH_DRAG_DOT. In image painting this
won't restore any mesh, so better have a name that is directly linked to
what the flag actually does.
Fix T37694: cycles particles emitter object rendering when it shouldn't.

This was broken by a recent bugfix for T37159.
Node Previews:
Removed USE_HIDDEN_PREVIEW from source code as it is now deprecated.
The feature was introduced during project mango to quickly hide previews, now that the previews are hidden by default this feature has no need.
Inside the DNA the flag is still visible in comment, this way no one will reuse that value as it could have some side effects

Jeroen & Monique
 - At Mind -
Missed one usage of use_hidden_preview.
add new UV editor edge theme colors to preset themes
Fix T37753: encapsulated the creation of the source ID into one function to ensure the id is always created correctly
Python API: when OIIO is disabled use the same version format.
DNA Deprecation: add DNA_DEPRECATED_GCC_POISON for enum/structs.

also fully remove freestyle raycasting_algorithm
CMake: report messages as status (else ccmake treats like an error)
Style changes to refactor commit.
Style Cleanup
Fix for fix: Paths and copying object

Fix for T37471 made path copying modify local paths,
now apply the same logic used for save-as.
Mempool/Memarena: hint for unlikely conditions
Fix for off-by-one regression in D41

making the window larger was using incorrect factor leaving a black bar
on the window edge.
Screen Resize: minor code cleanup
Fix T37463: Increasing window size would add space around menu header