Completely re-write Journal Voucher Module

Fixes  #108 .

In this PR:
 - Complete redesign of the Journal Voucher UI
 - Complete re-write of the journal voucher code
 - Fix bug with creating transaction ids for the posting journal using `/max_trans/`

*Note:*
Journal Vouchers does not play well with exchange rates.  Our exchange rate module + service needs to be completely rethought in order to make this happen properly.  However, I am submitting this so that I can focus on more diverse issues and hopefully open that up for others to help solve.