Make all avaiable checks and set the header filter for including files

In favor of https://github.com/otrv4/pidgin-otrng/commit/23629e15d77c78f70166ef3b87f85a08d518167b#r35026447

WIP related to #112

WIP related to #112

WIP related to #112

It's not necessary for now that signal

This code is WIP and need revision
- Checks if the client conversation is encrypted
- Converts client conversation to plugin conversation in a better way
- Related to #65 and #69

- Get all OTR conversations and close each one
- Related to #65 and #69

In favor of https://github.com/otrv4/pidgin-otrng/commit/11bdc1a66a8c7ddafb9b3b55b11a63c10152d157#r34626655

- When one of the users close Pidgin unexpectedly close the OTR session
- Related to #65 and #69

Implementing a configuration property to evaluate if the user want to show the SSID on conversation screen