/bitcoin/bips/blob/master/bip-0022.mediawiki
    https://github.com/bitcoin/bips/blob/master/bip-0023.mediawiki
    https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki#getblocktemplate_changes
    https://github.com/bitcoin/bips/blob/master/bip-0145.mediawiki

Arguments:
1. template_request            (json object, required) Format of the template
     {
       "mode": "str",          (string, optional) This must be set to "template", "proposal" (see BIP 23), or omitted
       "capabilities": [  