feat(protocol): Added configuration part for all network shapes of Handshake protocol

[arepala-uml]

1. Followed the HSD protocol/networks.js and added all the necessary constants & configs.
2. Added the defnition of Network struct and added some of the helper functions for this Network. (https://github.com/handshake-org/hsd/blob/master/lib/protocol/network.js)
3. Defined a Networks map and configured all the shapes mainnet, testnet, regtest & simnet by taking reference as (https://github.com/handshake-org/hsd/blob/master/lib/protocol/networks.js).
4. Completed the testnet definition part by taking the reference from (https://github.com/handshake-org/hsd/blob/698e252ebc7b5c1dd0a9587e342fdd153d020ae4/lib/protocol/networks.js#L647)

[arepala-uml]

@wolf31o2 @agaffney I have made changes by taking the reference from HSD protocol part and added only one shape(testnet) and need to add for remaining shapes. I want to ask your suggestions like if any changes or required or I am going in wrong way. Please help me and I have raised PR for whatever the changes which I have made till now.