* Add. BLF indication for call forward.
To display general status of CallForward use blf like `forward+<extension>`
To display status for specific phone number use blf like `forward+<extension>/<number>`
* Fix. Escape variable in regex expression.
* Fix. Sync DND and CF blf.
* Add. `blf_subscribe` service which can handle all custom subscriptions.
To run for specific protocol it possible run as `luarun blf_subscribe.lua <PROTO>`
Alexey Melnichuk