use "Gronnga" notation to .txt and .po
Merge pull request #125 from cosmo0920/use-Groonga-notation-doc-community

use "Gronnga" notation to .txt and .po

Patch by cosmo. Thanks!!!
doc: remove a reference to a removed command

This fix the following warning:

    doc/source/news/1.0.x.txt:120: WARNING: unknown document: /reference/executables/grntest
doc: remove needless files

We will not implement them.
doc: update files
doc: add missing label

This suppresses the following warning:

    doc/source/reference/functions/sub_filter.txt:117: WARNING: undefined label: select-table (if the link has no caption the label must precede a section header)
doc: add missing label

It suppresses the following warning:

    doc/source/reference/normalizers.txt:21: WARNING: undefined label: table-create-normalizer (if the link has no caption the label must precede a section header)