v0.9.15

Object picking contribution from Ruan Moolman - intergrated into new Phoria.View. - Also includes utility methods to convert planer to polar and back plus poly/line intersection tests.
Added picking demo page test0p.html - showing highlight when cube is picked.

Moved mouse events into Phoria.View class. - phoria-view.js is an optional include to provide additional functionality such as high-level mouse event handling and object picking.

Upgrade to latest gl-matrix r235 - NOTE translation is now always along global axis - not object local. Fixed up tests to reflect changes.

Rotation example test0q.html using Quarternions to rotate in either World or Local object axis and avoiding gimbal-lock.

Optimization to calculate average Z during main scene processing loop

Added methods to retrieve screen coordinates bounding rectangle and world coordinates bounding cube for an entity.