the Unlink event was replace by Bridge unlink
add a dispatch filter class for call forms
add handle_dial to the call_form dispatch_filter

the call_form dial event is not triggered by the userevent_user but by the dial
remove ami_channelupdate from amiinterpret it does nothing
remove sheetsend from interface_info

only the dispatch filter calls sheetsend now
add DispatchFilter to context
handle dials to call that are going in a queue or group
remove unused function currentstatus
remove useless userevent agent
use the dispatch filter instead of calling sheetsend directly
add alot of logging in callform triggering events
add a VariableAggregator to track call form variables by uniqueid
track call form variables by uniqueid

Remove extra_data from the Channel class
Add a VariableAggregator to the call_forms package
Quickfix the ChannelDAO that rely on call form variables to get the caller ID of a channel
Change sheets to work with unique ids instead of channels

This _BIG_ change is the result of failing to get a working call form flow when
basing calls on the channel name. Local channels and masquerades made it impossible
to follow a simple call to a queue.

Using the uniqueid remove all this mess since a call form has the same unique id
at each step of it's lifetime.

This change also remove the only use of the xivo_manager_inherit patch in asterisk
cleanup the cache when a call is complete
the keys desttype and destid have to be present

the user match function sends to everyone on an empty dict
remove the sheet_cleanup callback
Merge branch '4628-call-form-variables'