Quality Categories deserves its own file - not in Developer Guide

[SteveMacenski]

This section is quite long and not really on the same topic as the rest of the developer guide. I think this is a good candidate to be Quality Categories Guide page in addition, in the contribution section.

[maryaB-osr]

@SteveMacenski you're right, that section doesn't belong in the developer guide, it's just there until the associated REP is released, which will be in a week or two.

This PR will get rid of it