Add cleanup by age feature

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.

![screenshot 2014-08-19 00 29 59](https://cloud.githubusercontent.com/assets/994805/3959602/be31359e-272f-11e4-9a35-dfd83c6d0ef8.png)

Added/Updated the tests suite to reflect changes.