Add a tool to create a "timeslice" element #1979
Description
Add a tool allowing to create a "timeslice" element (which seems to be an OccurrenceUsage) inside an OccurrenceDef node or a OccurrenceUsage (or one of its sub-type) node.
As always, check in the SysMLv2 specification what are the consequences of the creation of such elements (elements to create, properties to set, implicit relations)