Unclear which flags are used by which roles

Describe the bug

Currently, it isn't easy to determine which flags (e.g. -maxTicketEV) are used by which role (e.g. -broadcaster or -orchestrator)

To Reproduce

1. Run ./livepeer --help
2. See a number of flags, with descriptions of how to use them e.g.:

  -maxTicketEV string
    	The maximum acceptable expected value for PM tickets (default "3000000000000")

3. Be confused about whether this flag is to be used with -broadcaster role or -orchestrator role.
4. Try running ./livepeer with the -orchestrator flag and also -maxTicketEV
5. Discover that setting the -maxTicketEV in this case is ignored
6. Be confused about why it didn't throw an error saying "you can't use -maxTicketEV with -orchestrator" (or something similar)

Expected behavior

I expect it to be made clear (e.g. in --help) which flags can influence the operations of which role.

Also, if I use a flag with a role where the role ignores the flag, I at least expect to be warned about it :)

Start by running ./livepeer --help and tracing how role flags such as -broadcaster, -orchestrator, and -maxTicketEV are registered and processed. Done means the help output identifies each flag's applicable role and using an irrelevant flag either warns or reports an error instead of silently ignoring it.