Structural Refactor of the bot

[LightDestory]

The current logic is not optimal, it depends on strings and so on.

For example the read_md, informative_callback relies on actual filenames that are binded to commands. Moreover some strings are hardcoded in places where it is impossible to get the language_code provided by Telegram thanks to the Update instance.

Hardcoded texts are used to run tests too...

My suggestion is to develop from scratch with modularity as main target.