Gather individual permissions into sensible roles.

[ScottArbeit]

Each server endpoint has a unique permission assigned to it.

For ease-of-use, those individual permissions should be gathered into default roles for repository owners to assign to users.

These roles should include:

• Admin
• Contributor
• Reader
• others as we think of them.

Eventually, we want repository owners to be able to create custom roles by choosing which permissions to include. Make sure the data schema handles that feature.