Make sure that an existing meta method is not overwritten when -meta_name is passed to Moose

This addresses RT #98488.
Add docs for -meta_name import option
Merge branch 'pr/90'

This addresses RT #98488.

Note that there is no bug here. By default, a class will still inherit a meta method from Moose::Object. However, if you subclass a different parent (with its own meta) you will get that meta method instead.