dotNAV: Add option to return subdomains from a name

[aguycalled]

@sakdeniz requested to add the option to the RPC command resolvename to return a name's subdomain.

• Required changes in navcoin-core
• Required changes in electrumx
• Implement resolve name changes navcoin-js#7
• Update testnet infrastructure infrastructure#1
• Testing and confirmation from @sakdeniz
• Update mainnet infrastructure

[aguycalled]

@sakdeniz the changes have been implemented, could you confirm they work?

[sakdeniz]

I will test it soon.

[sakdeniz]

Tested, its works as expected.