FIX: handling of very long chat messages

[kodaline]

Description

Handle of very long chat messages

The following files were changed:

• cheshire_cat.py: input message is split at MAX_TEXT_INPUT tokens saving what exceeds in declarative memory
• rabbit_hole.py: new method string_to_docs to just convert strings in documents

relates to issue #334

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas

[kodaline]

Hi @pieroit , here is a way to handle very long chat messages, splitting them at MAX_TEXT_INPUT and sending the rest to the cat's declarative memory as discussed

[pieroit]

@kodaline we need to revert the develop branch from async/await back to threadpool, because too many things are getting buggy.
As soon as that part is finished I'll review this PR, please leave open ;)

[pieroit]

Thanks!!