WIP: Use simpler syntax in grammar names

[Mouq]

Things like token package_declarator:sym<grammar> become token package_declarator:grammar

The only nits here are that the line
<?sigil> <var=.LANG('MAIN', 'term:variable')>
which seems like it should work, doesn't in NQP, and must be:
<?sigil> <var=.LANG('MAIN', 'term:variable<1>')>
and that we can't use
method package_declarator:grammar($/)
but instead
method package_declarator:grammar ($/)
because NQP (and Perl) will think ($/) is the value of the :grammar colonpair

[Mouq]

This causes some failures in spectest. Consider this PR a WIP – it's current purpose is to point out the possibility, ask for the possibility's consideration, and do most of the work implementing it

[Mouq]

Honestly, this is unnecessary and purely cosmetic, other than causing some issues with name look-up. Closing for lack of usefulness