testcase: use the output of vochain.NewGenesis to start a chain

[randomshinichi]

dvotecli genesis/vochain.NewGenesis() outputs a valid genesis.json (where Tendermint JSON wants integers represented as strings) but its output is never used in integration tests to spin up a node.

As a result, https://github.com/vocdoni/vocdoni-node/blob/master/vochain/genesis.go has invalid JSON where some integers are formatted as integers and some integers are formatted in the tmjson style (integers as strings). Unfortunately this breaks consensus which is why we haven't done this yet.

2 possible solutions:

• define genesis not as a hardcoded json, but as a struct, which will then be used to directly run the node, or formatted into a json for external use (e.g. integration tests which require a json)
• Have a test case which uses the output of dvotecli genesis to start a chain (slow)