Add option to MEArecRawIO for loading only recordings or only sorting data

[h-mayorquin]

Right now MEArecRawIO loads all the data (recording and sorting) by default. This PR leaves that default as it is but also adds the option of only loading recording or sorting data with a boolean value at __init__.

With this, the intialization of the object -specially the recoder- should be lighter as it does not need to go through the spiking data in mearec.

I added tests for both of these modes.

[alejoe91]

Thanks @h-mayorquin! This will make reading MEArec files much faster and getting the number of channels in a more robust way

[JuliaSprenger]

Hi @h-mayorquin Could you also add the new arguments to the MeaRecIO, to be available also for the non-rawio?

[h-mayorquin]

@JuliaSprenger should be done.

[DradeAW]

If this is done, could it be merged? :)

Thanks

[h-mayorquin]

Edit: Mistake comment.

[samuelgarcia]

This is cool.
Here in neo we do not have the naming recording which is very very confusing.
I would change it to load_analogsignal'

[h-mayorquin]

I changed load_recordings to load_analogsignal

[h-mayorquin]

I implemented @samuelgarcia feedback now.

[JuliaSprenger]

@samuelgarcia Are you happy with the changes? Then feel to merge.

[samuelgarcia]

merci @h-mayorquin