Add option to exclude the examples.
Add --jom and --jobs options.

--jom will use jom instead of nmake for msvc builds
--jobs will set the number of build jobs (-jN passed to make or jom)
Oops, we need to actually use OPTION_JOBS too.
Fix path updates to not store the lower() version of the original path values.
Various additional build fixes and tweaks.

- Validate py_prefix and py_include_dir
- Add install_dir/bin to the PATH
- Set CMAKE_PREFIX_PATH to install_dir
- If QTDIR is set then use it for ALTERNATIVE_QT_INCLUDE_DIR
Merge pull request #12 from RobinD42/add-new-options

Add new options
Merge pull request #13 from RobinD42/more-build-tweaks

More build tweaks and fixes