Add cleanup by age feature

[miguelcnf]

This will allow a repo to have a cleanup by rpm build age option.

The idea behind it is that due to having a very large number of rpm builds being generated every day you might want to specify a max number days for rotation of each package instead of the max number of builds of the package.

In practice the cleanup method now performs both cleanup methods using a binary OR operation.

Changed the interface to have 2 sliders for each option with a 30 days max for the new cleanup by age method and set the cleanup by age default to 0 (NEVER) so that the same behaviour as before is maintained by default.

Added/Updated the tests suite to reflect changes.

[miguelcnf]

@heroldus any chance this can be looked at?

[heroldus]

Sorry, I forgot to merge your request. Done.

[miguelcnf]

Thanks!