why do we keep a civicrm_stripe_plans table? Can we remove it?

[jmcclelland]

I was just bitten by #103 again and after considering the code, it seems like we can eliminate this table.

Then, for every plan, we first query stripe to see if it exists and if it doesn't we create it.

It seems that the only purpose of the plans table is to avoid this extra query. But the cost is losing a recurring contribution if something gets out of sync.