Feature request: extend properties API data returned

[PaulBernier]

Current properties API return:

{"walletversion":"2.2.15-dev","walletapiversion":"2.0"}

I'd like to see additional information to be returned:

1. Boolean if the wallet is encrypted on disk or not
2. Boolean telling if the wallet is currently locked or not (and potentially the time it will be locked again?)
3. Information on the Factom network that instance of walletd is connected to. I'm thinking MAINNET, TESTNET, LOCAL, CUSTOM but maybe also the exact factomd endpoint it talks too could be useful.

All of those would allow better feedback to the end user, particularly if one wants to build a UI on top of walletd (which is my case with the FAT wallet).