Fix a bug that velocity gets screwed when entering materialized star

We observe a phenomenon that the warp velocity vector suddenly goes to
unexpected direction when we approach a randomly generated star which
is just materialized.  This was caused by referring to old position vector
in warp calculation method, which should be updated when the destination
CoordSys is altered in materializeStar().

We are also observing strange velocity behavior when warping to Sol,
but it seems due to another cause.
Fix space_debug.ssd had invalid orbit specification

Also made OrbitCS::readFile() report a warning if it could not find a
orbit with given name in the file.  This would make debug easy.
Fix star name for Rigil Kentaurus in space_debug.ssd
Change type of shader file name strings to gltestp::dstring

We should make all dynamic strings gltestp::dstring instead of
cpplib::dstring or std::string, since we need to export these string
types to extension DLLs.

Also added a typedef for "st" and shorthand type for std::vector<String>.
Add GLSL file name as TexSphere properties accessible from Squirrel
Add shaders for flat textured planets in randomly generated systems

Now they take effect of HDL exposure.