bux fix for custom upgrade streams

line 199: in case of custom upgrade streams, variable $signature contains the last value from the foreach cycle at line 130, not the core schema signature!

line 209: if we do not insert schema signatures for each custom stream, after install osTicket thinks it needs an upgrade and gets stuck (see function isUpgradePending() in class.ticket)
Merge pull request #854 from alpianon/patch-1

bug fix for custom upgrade streams

Reviewed-By: Jared Hancock <jared@osticket.com>