Omniwallet issues affecting Omniwallet REST client

[msgilligan]

This is a tracking issue for Omniwallet issues that will resolve issues in the Omniwallet REST client. This issues are listed in "priority to OmniJ" order:

1. Address-balance rate-limit issue: Multiple address-balance request returns zero BTC balances due to rate limit omniwallet#1507
2. Include reserved amount in /v2/address/addr query: address-balance request should return 'reserved' balances omniwallet#1511
3. Watch-only backup/export of Omniwallet addresses: Add watch-only backup/export of wallet addresses omniwallet#1287
4. Distinguish Divisible from Indivisible property type in address-balances: Distinguish divisible vs. indivisible values with numeric formatting. omniwallet#1235
5. Ability to query block hash along with block height: API /v1/system/revision.json should return block hash of recent block omniwallet#1504
6. Linkable URL on Omniwallet for showing an address-balance: GET URL for Omniwallet balance check omniwallet#1288