Spec file tidy

Some improvements to the spec file.

- I've defined a 'releasenumber' macro so that the release number only needs to be manually changed in one place, rather than three we had before (due to the change in versioning scheme).
- I'm combined directives that apply to the same file in the 'files' sections which should solve the warnings that are raised during the build about files appearing more than once.
- Sections breaks for better readability.

Test built successfully on both SL5 and SL6.