Reset Sets while modifying an existing group of sets of type PREFIX or SUFFIX

[scalbertm]

While modifying the name of a group, the number of sets to fill keeps increasing with each modification of the name and are not reset when modifying the group type.

Impact: ModelSlice.actions.changeGroup
This function needs to purge the deprecated sets (for instance by checking their validity with current group name and String.prototype.startsWith/endsWith)