Make get_data method on FOOOF, overloaded on FOOOFGroup, to replace get_all_data #140
Description
Right now you can use string indexing on FOOOFGroup objects in get_all_data, to return all data of a specified parameter.
It would be more consistent (across FOOOF objects, always having string indexing available) to have a get_data function defined on the FOOOF base object (so you could also use string indexing there), and then overload this in FOOOFGroup to act like what is currently get_all_data.
Note: this is straight-forward to add, though it's slightly annoying that this means there will be a get_data, different from get_data_info. This update should probably entail updating get_data_info (and the DataInfo object) to be called 'MetaData' (or something similar), to clearly differentiate them.