Some sip notify events don't have a content type, such as notifies that only update the caller id info of a call.

add core-db-inner-pre-trans-execute and core-db-inner-post-trans-execute to switch.conf.xml to wrap sql stmts inside the meat of the core transactions

add core-db-pre-trans-execute and core-db-post-trans-execute to switch.conf.xml to wrap sql stmts around the core transactions

add sip_require_timer=true variable to enable require timer on session refresh that breaks finicky endpoints

gsmopen: AT+CREG erratic behavior does no more give errors or warnings when badly formatted unsolicited signaling

This lets you specify a FS_SOUNDS_DIR in which to look for the sound
tarballs.  This makes it easier to use git clean -fdx without
downloading the sounds every time.