Move include of package name determination

To neatify the top level buildscript, move the include of the packaging
filename module to just before the include of the main packaging module.
Rationalize CMake scripts

Move versioning and build options from Config module to main
CMakeLists.txt script for clarity. Remove PackageFilename module,
copying its functionality into the main Packaging module.

Replace usage of CMAKE_{SOURCE,BINARY}_DIR with CAMP_{SOURCE,BINARY}_DIR
to avoid potential clashes if CAMP is embedded in another project.
Remove excess whitespace from CMake scripts
Add FATAL_ERROR argument to cmake_minimum_required calls

Add to ensure failure rather than warning on CMake 2.4 and earlier.
Remove check on CMake < 2.4.7

CAMP requires CMake 2.6 or higher and will fail if this requirement is
not met. The Mac OSX check on CMake 2.4 is thus obsolete, so remove it.