Rename everything Stasis-HTTP to ARI

This renames all files and API calls from several variants of
Stasis-HTTP to ARI including:
* Stasis-HTTP -> ARI
* STASIS_HTTP -> ARI
* stasis_http -> ari (ast_ari for global symbols, file names as well)
* stasis http -> ARI

Review: https://reviewboard.asterisk.org/r/2706/
(closes issue ASTERISK-22136)


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@395603 f38db490-d61c-443f-a65b-d21fe96a405b