Small fixes on BIDS datasets

[PierreGtch]

Issues I found while using these datasets:

• the ‘suffix’ should be ”epo”, not the datatype
• not useful to have datatypes=“eeg” by default
• sometimes the annotations are not set in _epo.fif files but we can still recover the event names using the events and event_id attributes

[PierreGtch]

The tests fail because I used the MOABB cache as BIDS dataset for the tests, but there is a small issue in the way they are saved at the moment.

For more details, see NeuroTechX/moabb#707

[bruAristimunha]

Does releasing moabb after merge solve the problem? It is only affected epoch data?

[bruAristimunha]

I looked again the file, it all the cache...

[PierreGtch]

Does releasing moabb after merge solve the problem? It is only affected epoch data?

It affects epochs and array epochs

[codecov]

Codecov Report

Attention: Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.

Project coverage is 87.29%. Comparing base (507103a) to head (e337366).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #704      +/-   ##
==========================================
- Coverage   87.30%   87.29%   -0.01%     
==========================================
  Files          78       78              
  Lines        7208     7219      +11     
==========================================
+ Hits         6293     6302       +9     
- Misses        915      917       +2