* add voucher service on storage node
* config field tag syntax, go routines for requests
* hook up voucher service in storagenode/peer.go
* add voucher config to testplanet
* add voucher config to testplanet
* add voucher response status INVALID, ACCEPTED, REJECTED
* add a test for vouchers service
* handle no row from GetValid, test it
* add trust pool to voucher service
* use trusted list to get satellites
* verify vouchers upon receipt
* test VerifyVoucher
* set up voucher service skeleton, basic test
* add VetNode db method
* basic test for VetNode
* encode and sign voucher functions
* fill out and sign vouchers
* test pass/fail voucher request
* match EncodeVoucher to other Encode functions
