Geometry sample refactor

Updates to Geometry sample:
* shaders moved to assets folder, reload them now by hitting return
* works on iOS. Double tap screen to change geoms.
* using geom::VertexNormalLines instead of the custom DebugMesh to draw normals. ~~This is how I ran into #587 (see in line note)~~ was fixed.
* Some cleanup and updates for changes to cinder/ glNext since this was originally written.
* reworked the giant double switch statement to not use geom::SourceRef's, which makes it much easier on the eyes.
* added params enum for choosing what type of texturing to use in phong shader.
* added @paulhoux 's fix from #586 for Helix params (sorry Paul, this was already stepping on the file so much I just thought this would be easier). 

~~Question: the stripes.jpg is loaded and bound, but isn't actually used for drawing. Do we need this in there, or should it be removed?~~ keeping, it helps to show some issues differently.