replaced prototyped pseudo-private functions with file-scoped functions in the module core

Signed-off-by: Ayudh Das <ayudh.d@gmail.com>
Improvements to CentralBody fragment shader.

Use an if statement instead of the crazy two-step-alpha-zeroing for
excluding a texture outside its extent of applicability.  Avoiding ifs is
sometimes good, but here it just overcomplicates the shader.  In theory,
with dynamic branching, the if could be faster, too.  I wasn't able to
measure any performance difference one way or the other from this change.

Treat alpha like the other properties (hue, gamma, etc.).  Only apply it
if it is not 1.0.

Removing debugging feature of showing texture boundaries.
TileCoordinatesImageryProvider does a better job of that anyway.
removed unnecessary comments and fixed the failing test case

Signed-off-by: Ayudh Das <ayudh.d@gmail.com>
Added cull to DrawCommand
Merge pull request #733 from AnalyticalGraphicsInc/cull

Terrain performance improvement
Merge pull request #727 from ayudhDas/issue-705

replaced prototyped pseudo-private functions with file-scoped functions ...
Add ayudhDas, his first pull request was #727
Merge master to cv
DynamicPath cleanup

Backout workaround for #602 which is no longer needed because the initial problem was fixed with #725
Merge pull request #729 from AnalyticalGraphicsInc/simplifyCBFS

Improvements to CentralBody fragment shader.
Merge pull request #725 from AnalyticalGraphicsInc/cv

Columbus view cleanup
Merged master to batching