session: divide command between new empty sessions and glob to add from the pool

Add new parameters:

• -n or --new to create a new empty session (this was the behavior until now)
• -c or --create plus two globs for package name and version (space separated, must be quoted) to create a new session and add given packages that match the glob pattern from the pool
• We remove -a and --add-all, since it can be done now with -c * *