subtitle api: translation - storing result

hard-coded as english-to-italian
subtitle api: making process_json indpendent
subtitle api: making process_json indpendent - part2

adding return value
subtitle api: translation - returning new subtitle_id

this is so GUI applications can redirect to new id
subtitle class: inherit from subtitle api class

subtitle api class inherits from basehandler
subtitle class: adding translate api
subtitle display: adding translate button