Distorted Android

Introduce DistortedRenderable, a base class for Texture and Framebuffer

Minor

Some fixes for issues discovered by the Multiblur app.

Beginnings of the 'Multiblur' app.

BLUR: implemented caching of the BLUR kernels.

Minor progress with Gaussian. Still need to cache the Weights and Offests tables.

Separable Gaussian Blur with linear sampling done.

Linear sampling implemented - i.e. blurring by a (2N+1)x(2N+1) gaussian kernel (centeral pixel + N pixels in each direction) requires exactly 2N + (N%2==1 ? 4:2) texture fetches.

Precompute the standard normal distribution.

minor.

Separable Box blur fully works now!