Make HACKING.rst DRYer and turn into rst file

Rename HACKING to HACKING.rst since it is a rst file and
reference the OpenStack hacking guide and remove
duplicated entries.

Change-Id: I9994594c7f8cb0f011d949b273bea08c68985e16
Fix trustee/trustor definitions

The trustee is the person consuming the trust, the trustor is the person
who creates the trust.

Change-Id: I4d6c4b4f14c0dfcb3b41cd3e37aecd01487442fd
Merge "Fix trustee/trustor definitions"
Merge "Make HACKING.rst DRYer and turn into rst file"