ENH add data loader for camcan dataset + add event description into info

[CedricAllain]

1. alphacsc/datasets/camcan.py: new file, add a data loader function with default pre-processing parameters
2. alphacsc/datasets/mne_data.py: add an event description dictionary in info['event_info']

[CedricAllain]

We need to discuss where to put this code as alphacsc is probably not a great fit

Indeed, maybe it is not really appropriate. I did this as there is a data loader of HCP in datasets/hcp.py.

[codecov-commenter]

Codecov Report

Merging #102 (16592c5) into master (1e8cf32) will increase coverage by 0.05%. The diff coverage is n/a.

:exclamation: Current head 16592c5 differs from pull request most recent head e6ebbd0. Consider uploading reports for the commit e6ebbd0 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #102      +/-   ##
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+ Coverage   82.09%   82.14%   +0.05%     
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  Files          22       22              
  Lines        2166     2172       +6     
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+ Hits         1778     1784       +6     
  Misses        388      388              

[agramfort]

to me the hcp loader should not be present here or at least not using hard coded path. There is no chance this hcp code is working for anyone.