Add auto-proxy feature

[jdcasey]

allow auto-creation of group/repository/deploy-point on-demand (will be configured automatically first time URL is hit). Also allow automatically proxying repositories/groups/deploy-points on a remote AProx instance...

Allow deploy-through to deploy artifacts to remote AProx deploy points?

[jdcasey]

Should auto-detect available endpoints on upstream repository managers, when possible.

[jdcasey]

Will leave this advanced option for autoproxying to a later feature.