Implement Go-XRouter logic in JS

[shrnkld]

To do:

• Implement xrGetBlock call
• Implement xrGetBlocks call
• Implement xrGetTransaction call
• Implement xrGetTransactions call
• Implement xrDecodeTransaction call
• Implement xrSendTransaction call
• Separate out raw calls which return all responses rather than just the most common
• Verify signatures of responses
• Remove redundant network object (network params are duplicated in the code and need to be moved to one central place)
• Implement xrService call
• Add events that the user can subscribe to rather than using callbacks like logInfo and logErr
• Add unit tests
• Create XRouter server type
• Create ServiceNode type
• Create Service Type
• Implement xrGetBlockCount call
• Implement xrGetBlockHash call
• Connect via p2p network
• Handle snp messages and build snode lists from xrouter configs