WorldForge::wfmath

A number of minor fixes.

The headers have been cleaned up to include fewer system headers and dependencies, and keep the namespace a bit cleaner.

A bug has been fixed that caused orientation data to become corrupted.

The template code has been updated to work with
gcc 4.2 and later.

The Quaternion class has been modified so that in a number of cases when it is initialised from data that would result in corruption, its valid flag is cleared. Many arithmetic operator functions have been reimplemented to make them more efficient and more compact.