fix!: EntityOwner::constant(), Utilities::stripName() etc.

- fix EntityOwner::constant() violates character restrictions
- Utilities::stripName() was broken in multiple ways. It has been
  changed into a true, reversible escaping algorithm and subsequently
  renamed into Utilities::escapeName().
- Utilities::unescapeName() is introduced.

BREAKING CHANGE: This commit will break applications which either
- rely on the names of device status PVs for devices which contain
  illegal characters (e.g. when using a CDD directly instead of a
  dmap file alias), or
- use Utilities::stripName() directly.