Port english version of managing data page for REST.
Port english version of buckets page for REST.
Port english version of object storages page for REST.
Port english version of file storages page for REST.
Remove redundant empty lines.
Fix layout.
Merge pull request #58 from shinsuke-nara/data

Port english version of managing data section for REST
Proofreading "Getting Started" (en and ja)
Merge branch 'develop'