Improvements of Material Preview

I have fixed the problem with Alpha in the preview that showed the rough glass material as black. This was probably caused by the recent Blender alpha changes.

I have also increased the brightness of the checker pattern in the background to see better the glass effects, etc.
Merge pull request #1 from DavidBluecame/experimental-dt

Improvements of Material Preview
Fix for preview crash
Exporting normals directly from blender to increase the consistency of the rendered geometry and resolve reflect/refract artifacts
Added git ignore for python precompiled files, just a convenience adition to the repo
Premultiply forced enabled, not optional anymore
Look & Feel changes for more visual clarity on general settings, checkboxes -> toggle buttons
Depth Map directly into blender buffers
Version bump 1.5.0-Stable
Additions to have a consistent z-buffer rendering into blender
Merge pull request #14 from DarkTide/master

Version bump, and some other fixes
Applied small changes to UI ( http://www.yafaray.org/node/581 )
Delete test for nodes in last commit
Solved mistake removed in last commit ( reported for 'wizofboz')
Fix suggest by 'samo' in http://www.yafaray.org/node/581
- Not enabled AA Passes with SPPM integrator method.
Refine AA changes for SPPM integrator
Sync SPPM parameters names to 'Core'
Expand IRE SPPM definition in Blender UI to 'Initial Radius Estimate'
Extend function for include light from 'add sun' or 'add skylight' in 'Sunsky' or Sunsky2  background mode.
Fix template list name for renderlayers
Expand checkSceneLights() function for use 'meshlights' with Bidirectional integrator
Review checkSceneLights() from 'wizofboz' feedback:
    - separate background check to objects.
    - add check for portal lights objects.
Merge branch 'master' of https://github.com/YafaRay/Blender-Exporter