Rework caching

[SamiMammouche]

Reproduction steps:

1. Create a strategy with a timeframe
2. Debug the get_price method which calls the get_cached_price method
3. You should see 3 calls being made to FMP for the same data

Refactor the caching and make it easier to understand. Get data from CSV cache and if it's not available, query FMP.

https://i.imgur.com/4AzSnex.png

[TristanFecteau]

To cache data locally, we should use https://pypi.org/project/appdirs/ (user_cache_dir)
Which will give us the working caching folder on every Win, MAC, Linux.

[TristanFecteau]

I also think we should cache json files, instead of csv, which would make it lighter on our code and the user's file system