Fix bash-based rpc tests

I fixed the bash-based rpc tests and added them to the travis config. That sounds more harmless than it is:

- I also fixed a few debug messages in the internal miner to use the new LogPrintf which prints into the log instead of stdout
- I fixed the regtest mode in the internal miner. In regtest mode, `setgenerate true 100` should mine 100 blocks instead of mining with 100 threads. The second commit ports the corresponding code from Bitcoin
- I amended chainparams to add a chain parameter which disables pseudorandom rewards. This special mode is used by the regtest mode to make it possible for the test-scripts to sanely calculate with block rewards. This change should not influence mainnet or testnet.