T2730
This diff creates a local transaction builder module to localize the bch-js portion of the transaction building process.
Temporary comparison checks have been added to sendXec which verifies that the txBuilder object matches after each stage of adding input, output and signing/building tx.
Relies on bitcoincashjs-lib for the eventual transaction building, and bip66 and bc-bip68 as per bch-js.
Pt 1/8 - Localize Transaction Builder module
Pt 2/8 - Deprecate BCH.TransactionBuilder in sendXec
Pt 3/8 - Add local TxBuilder to createToken
Pt 4/8 - Deprecate BCH.TransactionBuilder in createToken
Pt 5/8 - Add local TxBuilder to sendToken
Pt 6/8 - Deprecate BCH.TransactionBuilder in sendToken
Pt 7/8 - Add local TxBuilder to burnToken
Pt 8/8 - Deprecate BCH.TransactionBuilder in burnToken