Add resting state EEG experiments

[tmorshed]

PR to make a new experiment class eegnb.experiments.resting_state which includes "resting"-type tasks.

Progress:

• There is a class for rs experiments.

Issues:

• The BaseExperiment class handles the iti and soa between stimuli such that an iteration of events is assigned to one block, and does the win.flip() between trials. This causes the third and later beeps to not come through correctly.

Solution: either

• Fix the BaseClass such that parts of the iti/soa/block design are infer-able using added higher-level input.
• OR, base it off of aob.py wherein we do not use a binomial distribution, but rather a repetitive 0,1,0,1 stimulus parameter.
• Hotfix in the meantime: The rs.RestingState experiment overrides the load_stimulus() and present_stimulus() classes and even creates a custom run_ts() method to run the experiment. Will be reverted after the new implementation is brought forward.

[JohnGriffiths]

@tmorshed what is the future of this PR? Is it close to completion? Were there some structural issues with it still?