We currently allow for rbt options to be marked as deprecated, and we'll

display deprecation info in the documentation and help text for the option.

But we weren’t emitting any warnings when users actually passed them on

the command line. This change allows rbt to emit a deprecation warning

when a deprecated option is used.
This change also allows setting a replacement option and the version in

which the option will be removed. Our sphinx documentation building

functions and help text building logic have been updated to include these.
I decided to move our RBTools-specific option attributes out of

Option.attrs and made them direct attributes on the Option class

instead. This keeps a clearer separation from the argparse arguments

and lets us keep this information around after the Option is added to

the parser (previously we would strip all of our custom attributes

before adding an option to the parser). We also get easy typing on

these attributes now.
We also recently marked rbt login's --enable-logging as deprecated, and

this change defines its replacement (--debug) and removal version (6.0).

Tested rbt login -l saw the deprecation warning
Tested rbt login with options other than -l, saw no warnings
Ran unit tests.
Built docs and looked at options that have one or more of the custom

  RBTools attributes (config key, extended help, added in and the various

  deprecation related attributes).