Started work on a well-defined colour model.
Merge branch 'hotfix/github_issue_29' into feature/colour_model
More work on a well-defined colour model.

Prepared the colour classes to work with different colour models.
More work on a well-defined colour model.
Merge branch 'master' into feature/colour_model
More work on a well-defined colour model.

Modified the colour class templates to be palatable for g++.
Merge branch 'master' into feature/colour_model
More work on a well-defined colour model.
Merge remote-tracking branch 'povray/feature/colour_model' into develop
Auto-generated revision.txt is now ordered by version rather than purely chronologically.