centred position identifier

Created by: meguiraun

Currently whenever a centring finishes and is "valid", see here:

• a new centredPosId is created for that centring (pos1, pos2, pos42...) to serve as a name
• in addition, an id is also created (integer, for client-server communication, easier with integers and independent of the name structure).

The problem is that if a centring position (the whole object) is deleted, the next succesfull centring will be named based on the number of stored centrings, potentially the same name as the already existing ones, but the integer id will be increased.

Action: name (pos42) and id (42) should be created the same way, always +=1, no matter how many centrings have been done before