Expand Witnet Node Quick Start Guide (Docker) section

[Tommytrg]

• Add a warning explaining that the sensitive methods are enabled by default.
• Explain the supported transports for the JSONRPC.
• Add a tip explaining that if you leave a container running for ages on the official log driver without specifying a limit it could crash

[aesedepece]

The JSONRPC thing is overkill IMO. At least inasmuch 99% of the Docker users won't mess with the JSONRPC but only the CLI.

[aesedepece]

Different question is that the fact that the JSONRPC has multiple transports is probably missing its own place in the documentation, and the integration guide (the last section in the docs) is probably outdated to that sense.

[aesedepece]

Namely, here