better caching for isProgrammable

+ query isProgrammable once, keep as static bool for all to see.
+ since it's impossible to have a fixed function and a programmable context within one app, the check only needs to happen once, even a rendererCollection must be homogenous in this respect.
update checks for fixed function renderer

+ makes sure fixed function renderer checks for usingVerts rather than the position attribute when issuing draw commands.
+ uses fixedFunctionPositionAttribute to draw when using fixed function.