* Add. Handler for SUBSCRIBE method for call flow application.
Usage:
1. Run form fs_cli `luarun call_flow_subscribe`
2. Create new call flow extension and set feature code to `flow+<EXTENSION>`(e.g. `flow+401`).
3. Set on the phone BLF key to `flow+401`
This code based on `mod_valet_parking`.
* Add. prevent running 2 copy of script.
Remove some unused vars and simplify implementation.
* Fix. Use correct protocol for send event.
* Fix. Do escape SQL arguments
* Fix. escape `+` sign in call flow extension.
Problem that `mod_commands` may load after than `mod_callcenter` and there no function `global_getvar`
So current code just create database with name `INVALID COMMAND!.db`.
Problem when `opendir($dir)` returns `false` and then
while cycle adds many empty strings which produce in the end
```
/etc/freeswitch/tls
/etc/freeswitch/tls/
/etc/freeswitch/tls//
/etc/freeswitch/tls///
/etc/freeswitch/tls////
/etc/freeswitch/tls/////
/etc/freeswitch/tls//////
/etc/freeswitch/tls///////
```
* Add. Provision to Escene ES330/ES320
* Add. Look up Escene device by ext+domain.
* Update Escene template.
* Add. `provision` section in config.
Found than ES330 some time hangup when it try get software/core and get error from fusion.
Alexey Melnichuk