Add basic command-line completion for :Glaive

Addresses #8.
Loosen regex 'Glaive' => 'G\%[laive]'

glaive#Complete is triggered by any unambiguous prefix of ":Glaive", and
this needs to be taken into account in the regexes.
Add completion for flag handles (foci)
Add completion for list foci
Merge pull request #11 from glts/add-basic-Glaive-completion

Add basic command-line completion for :Glaive