Eliminate temREDUNDANT_SEND_MAX (RIPD-590):

The rules for when a SendMax is redundant are complicated. It is easier to always allow a SendMax and eliminate temREDUNDANT_SEND_MAX.

Reviewers: @JoelKatz, @scottschurr 
Thanks Scott. This work was done for RIPD-690 (https://ripplelabs.atlassian.net/browse/RIPD-690). I can't speak to the ramifications and I share your concerned. My understanding is that the rules for determining when a send max is redundant are too complicated and therefore we would be better off eliminating REDUNDANT_SEND_MAX and telling people is always safe to include it. Please see David's comment and let me know if you interpret his comment differently.