Fix RPC help output alignment

[random-zebra]

For tracking purpose.
The 'help' output of some RPC function appears to be misaligned.
REF: #955 (comment)

[CaveSpectre11]

It might be a good time to also set a line length standard for RPC output. 80 characters is a little antiquated; 132 should be okay, but given the code indenting... having the rpc output be no more than 120 characters per line might be a worthwhile standard to impose. (the lengths of lines when they wrap to multiple lines isn't very consistent).

[CaveSpectre11]

While technically it would be a different issue; it'll span through a lot of the same files: Need to add checks for pwalletMain == NULL where applicable.