Changes for master

[dvandyk]

Merges the following changes:

• use analysis.yaml instead of the (hidden) .analysis.yaml as the default name for an analysis files in eos-analysis
• run pyupgrade on python/eos/tasks.py
• provide means to specify optional required modules for every task (Unify importing of optional Python modules in eos.tasks #693)
• add a new subcommand eos-analysis init, which install the contents of eos/analysis-template into the current working directory
• check the names of kinematic variables in all observables against a whitelist (Check names of kinematic variables against a whitelist #750)
• improve the usage of GegenbauerPolynomial in classes PionLCDAs, AntiKaonLCDAs, and KaonLCDAs (in furtherance of addressing Potentially improve the interface to GegenbauerPolynomial #747)

[mreboud]

Thanks @dvandyk for these changes! I left comments.

[mreboud]

Can we merge this one @dvandyk?

[dvandyk]

Can we merge this one @dvandyk?

I think so!