doc grn_expr: use "Groonga" notation
doc edit_distance: use "Groonga" notation
doc geo_distance: use "Groonga" notation .txt and .po
doc indexing: use "Groonga" notation .po
doc tuning: use "Groonga" notation
doc output: use "Groonga" notation .po
doc grnslap: use "Groonga" and "GQTP" notation
doc groonga: use "Groonga" notation
Merge pull request #147 from cosmo0920/use-Groonga-notation-reference

doc: use "Groonga" notation

Patch by cosmo. Thanks!!!