Service: top-up process

[nkostoulas]

• Extend config to include top-up addr and top-up flag. Move staychain config in one category:

"staychain" : {
 "regtest" : ,
 "initTx" : ,
 "initScript" : ,
 "topupAddr" : ,
 "topupScript" : ,
}

• Attest client changes
  Examine cases we've been assuming single vin so far
  Do creation, signing for multiple inputs
  Unit-tests

• Attest service changes
  New DO_TOPUP state
  Fetch topup unspent and create attestation
  Fetch multiple sigs from clients
  Unit-tests

• Unit-test top-up scenario paying to new address

• Testing with txsigningtool (need additional -topupPk)

• Raise warnings when funds below some value && raise error when below maxFee allowed