Checkmk Werk 15231: Drop command line alias "cmk -P" for "mkp"

ID: 15231 Title: Drop command line alias "cmk -P" for "mkp" Component: Checks & agents Level: 1 Class: New feature Version: 2.2.0i1 The extension packages manager has been callable from the command line in three ways: LI: <tt>cmk -P [arguments]</tt> LI: <tt>check_mk -P [arguments]</tt> LI: <tt>mkp [arguments]</tt> We no longer support the first ones, and only keep the <tt>mkp</tt> command. This unification reduces confusion, eases documentation, and increases maintainability.