Add PageMeta class

Read and save, delete pageMeta data
Complete test (partial)
Modify tests
Modify YamlPageMeta

Add param to constructor.
Modify depth to 2 of key at get.
Complete tests.

Add test data dir
Use YamlPageMeta where meta_read using
Modify PageMetaInterface and tests
Complete new tests
Modify using meta_read
Add method to PageMetaInterface: getPage.

Implement the method.
Write and complete tests
Fix taking page name at bootstrap
Delete meta_read/write function.

Because, PageMetaInterface is debut!
Modify reading page meta data at page_meta.inc.php
Modify .gitignore

Ignore haik-contents/meta/*.yml
Add method to PageMetaInterface: toYaml

toYaml returns yaml string of page meta data.
* Add and Complete tests
Modify YamlPageMeta

* Sync YamlPageMeta::setAll and PageMetaInterface
* Specify depth of dumping YAML at YamlPageMeta::toYaml
Add Yaml formatted page meta editor

* Add to edit action
* Add form control: textarea
Merge remote-tracking branch 'origin/yaml-ize' into fix-admin-less