[Refactor] Update magneticAnomalyActive bool to ScriptFlags

[zquestz]

This resolves the code debt introduced by passing the magneticAnomalyActive bool around instead of the current ScriptFlags set. This should be much cleaner to maintain for future hard forks.

[tyler-smith]

This looks great. I made issue #60 to track the TODO items

I made a branch that abstracts all the bitmask AND mask checks into HasFlag methods. Let me know what you think, and if you think it's good we can include it in this PR if you want. https://github.com/gcash/bchd/compare/txscript...TS_txscript?expand=1

[zquestz]

Your changes look great. Go ahead an throw those commits in this PR and lets merge them together =)

[tyler-smith]

Cool, your changes lgtm so I'll mark it as Accepted. Merge when you and/or @cpacia think my change is ready.