Add support for the 'verifymessage' RPC command
fixing tests
optionally allow to pass in the path to the bitcoin.conf file if it is at a non-standard path
assert that we are really in the testnet
Allow use of https
Allow use of https
There isn't always an error key in resp dict

There isn't always an error key in resp dict, particulary if there is no error.
fix bug when error: null in json reply

Return result when receiving a reply where the key "error" is null, like
this one: {"result":"some result here","error":null,"id":1}. Without
this change, the result would not be returned even though no error
happened.