Improve ability to initialize Stata automatically

[hugetim]

• Find most common Stata18 Windows path automatically (currently blocked due to a change in Stata18's Windows registry setup)
• Find most common Stata Mac path automatically (bug in legacy code prevents edition discovery)
• Initialize Stata when given a path but not an edition in config file (currently only works for default 'be' edition)

[hugetim]

Resolved by 1b179e7, 76dee3d, and a4c68fc.