Changes to instance naming:

Changes to instance naming:

* Engine is now appended to instance name (wording.appendEngine)
* Parts of the instance name can be used in forcedCfg. For example
on an instance called stable-master-pgsql %instancename:1% is replaced
with 'master'
* New flag 'purpose' replaces 'integration'. Purpose can be 'integration',
'stable' or 'review'. Instance names reflect this.
* A type of instance can be specified to `mdk backport` (i.e., 'integration',
'review' or 'stable'. If none is given the type of the current instance is
used.