ARI/AMI: Update versions; update UPGRADE/CHANGES notes for 12.1.0 changes

Due to backwards compatible changes made to AMI/ARI, the version needs to
be bumped to 1.1.0/2.1.0, respectively.
........

Merged revisions 407402 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@407407 f38db490-d61c-443f-a65b-d21fe96a405b