Remove ColorTable.hxx
The ColorTable header was split into two files: the normal
ColorTable.h header and a secondary ColorTable.hxx that
contains the ColorTable "implementation." This is so you
can include ColorTable.h without necessarily having to use
a device compiler.
However, this implementation is confusing. So ColorTable.hxx
has been deleted and moved elsewhere. This means that the
Sample method implementation is moved to ColorTable.cxx.
Compiling these methods into the library makes more sense
anyway. It also means that the Map methods have been
moved to free functions and placed in a ColorTableMap.h
header.