Clean up and make HACKING.rst point to openstack-dev/hacking

Instead of having a full local copy of HACKING Reference the OpenStack
hacking guide (openstack-dev/hacking) and remove duplicate sections.

Change-Id: Iaabc27c42d74b7441c17e63db15724f64114620b
Remove uncessary code related to nova start/stop

'nova start' and 'nova stop' actually send request with 'os-start'
and 'os-stop', instead of 'start' and 'stop'.

Change-Id: I1472e1b648dae8f3b281a113adb60421a00e5a48
Add AgregatesManager.get()

utils.find_resource() uses manager.get() as part of converting Resource
names to IDs.  AggregatesManager had get_details() instead of get().

Add AggregatesManager.get(), leaving .get_details() in place for backward
API compatibility.

Bug: 1200341

Change-Id: I7d238bbe43e1760e31f1a9ba783c668246f20844
Merge "Remove uncessary code related to nova start/stop"
Merge "Clean up and make HACKING.rst point to openstack-dev/hacking"
Merge "Add AgregatesManager.get()"