Enhanced Python API

Feature suggestions from @aiwieder:

• An available_tags property on the AnalysisData object, e.g.

datasets.available_tags["polarity"] == {"magup", "magdown"}
datasets.available_tags["years"] == {"2015", "2017", "2016", "2018"}

• A samples property on the AnalysisData object that returns a list of objects in information about the sample (maybe a dataclass) e.g.

for sample in datasets.samples:
    print(sample.name, sample.version, sample.analysis, sample.wg, sample.tags)