Replace GLWallpaperService with a simpler method

Android's GLSurfaceView is now used. GLWallpaperService (which was
basically a carbon copy of GLSurfaceView anyway) has been removed.

Implementation is from http://www.learnopengles.com
Init GLSurfaceView in onCreate(), not constructor
Remove ContextFactory, use GLSurfaceView default

ContextFactory is more or less identical to the internal
DefaultContextFactory that GLSurfaceView uses by default.
Destroy renderer at original spot

Destroying it in onSurfaceDestroyed() seemed to create some problems.
Merge branch 'master' into simple-wallpaperservice
Merge remote-tracking branch 'origin/master' into simple-wallpaperservice
Fix cube map shader crash with multiple lights

"L" was declared multiple times (once for each light). Now it will be
declared only once.

Fixes #272
Merge pull request #268 from MasDennis/simple-wallpaperservice

Replace Robert Green's GLWallpaperService with simpler class

Android's GLSurfaceView is now used. GLWallpaperService (which was
basically a carbon copy of GLSurfaceView anyway) has been removed.
Update src/rajawali/materials/SphereMapMaterial.java

Fix the same issue on CubMapMaterial.
Info: https://github.com/MasDennis/Rajawali/issues/272
Merge pull request #273 from sesese/patch-1

Fix SphereMapMaterial crash with multiple lights
Remove duplicate text in README
Added mManageMaterial to specify whether a BaseObject3D will reload its
materials automatically or not. If many objects share the same material
then having each reload their material will cause lengthy and
unnecessary shader compiles. With this, one can avoid the redundant
compiles and simple re-assign the material to each affected object in
onSurfaceCreated().
Merge pull request #281 from jgooderham/master

material management flag
fix erroneous conversion to radians
Merge pull request #283 from nashira/master

erroneous conversion to radians
Remove preference classes

The preferences are outside the scope of this library (3-D framework),
and I have no desire to support or maintain them here.

Plenty of slider and color preference implementations can be found
around the web. Examples:

https://github.com/jayschwa/AndroidSliderPreference
https://github.com/jayschwa/android-ColorPickerPreference
Remove unused import
Make Lint happy

Lint was displeased with keepclasseswithmembernames and said it should
be replaced with keepclasseswithmembers.
Disabled blending during color-picking render pass
Merge pull request #286 from rpicolet/master

Fixes #285