Use trusted validators median fee

This fixes the problem with people running validators that don't use the temporary new fee floor. Note that this has already been deployed:
https://github.com/ripple/rippled/commits/release

Reviewers: @JoelKatz @tdfischer
Approvers: @rec @nbougalis 
Forget that.  fees and fees2 are not scalar numbers, but some sort of collection... my mistake!