Support multiple indexes including a nested index and multiple keywords query

For example:

    select TABLE \
       --match_columns "column || nested.column" \
       --query "KERYWORD1 KEYROWRD2"

See the following added tests for details.

  * test/command/suite/select/index/nested/match_columns/last/and.test
  * test/command/suite/select/index/nested/match_columns/middle/and.test
test: remove memcached API tests

We can't maintain it.
test http: update status code
Use ii functions to resolve search results by nested index search

It fixes the following test broken by
89c5576a310aa86783804f959285874ac388d117:

  * test/command/suite/select/index/nested/by_column/match/and.test

Detail:

    [30] select/index/nested/by_column/match
      and                                                           1.0461s [failed]
    ================================================================================
    --- (expected)
    +++ (actual)
    @@ -29,35 +29,30 @@
      select Files   --filter '_key @^ "/home/" && owner.hobby @ "programming"'   --output_columns '_key, owner, owner.hobby'
      [
        [
          0,
          0.0,
          0.0
        ],
        [
          [
            [
    ?         1
    ?         0
            ],
            [
              [
                "_key",
                "ShortText"
              ],
              [
                "owner",
                "Users"
              ],
              [
                "owner.hobby",
                "ShortText"
              ]
    -       ],
    -       [
    -         "/home/alice/.zshrc",
    -         "Alice",
    -         "programming"
            ]
          ]
        ]
      ]

See also: https://travis-ci.org/groonga/groonga/jobs/16860080
Add missing explicit initialization
Don't use res_add() in expr.c

expr.c should use grn_ii_posting_add() that calls res_add() in ii.c
because it is an exported function. We should not use copy & paste
development.
Use bulk reader macro instead of explicit cast
Don't use index for empty query

Because we can't use index with empty query. Groonga's table doesn't
accept empty key. So we can't register a document to index with empty
key.

[groonga-dev,02052]

Reported by Naoya Murakami. Thanks!!!
doc news: fix typo

envri nment ->
environment
   ^^^
Merge pull request #149 from cosmo0920/fix-typo-news-en

doc news: fix typo

Patch by cosmo0920. Thanks!!!
doc install: use "Groonga" notation
Merge pull request #150 from cosmo0920/use-Groonga-notation-installation

doc install: use "Groonga" notation

Patch by cosmo. Thanks!!!
Add normalizer accessor to grn_snip

New functions:

  * grn_snip_set_normalizer()
  * grn_snip_get_normalizer()
Support adding conditions to existing grn_snip from grn_expr

New function:

  * grn_expr_snip_add_conditions()
snippet_html: use new grn_snip related API
deb: fix info tags which lintian reports

I: package-contains-no-arch-dependent-files

See http://lintian.debian.org/tags/package-contains-no-arch-dependent-files.html
deb: remove needless period in Description: field

I:description-synopsis-might-not-be-phrased-properly
deb: update long description about protocol
deb: fix a typo
deb: use source:Version when Architecture: all depends Architecture: any package

See http://lintian.debian.org/tags/not-binnmuable-all-depends-any.html