We received a bug report that the web login option was not working for

the rbt post command. Upon investigation, it was found that web login only

actually worked correctly for rbt login. It also worked for commands that

call get_authenticated_session before doing any requests that require

authentication (such as rbt status), but this only worked when the

WEB_LOGIN option was set in .reviewboardrc, not when the option was

passed through the command line.
This change is the beginning in a series of ones that allow web login to be

used for authentication when using any rbt command. This change only

generalizes command options, it doesn't actually implement web login on the

commands (that happens in /r/14575 and /r/14576).
We make the web login option a general server option, instead of only

applying to the login command. The command's long form has been renamed to

--web-login instead of just --web, but we keep the existing -w/--web

option on the login command for compatibility and since -w is a

convenient short-form of the option.
Similarly, we make the open browser option a general one, instead of only

applying to the login and post commands. In the future, any commands that

navigate to a URL can make use of this option to open URLs automatically in a

browser. It has also been renamed to --open-browser, but keeping the old

-o/--open version like we did for the --web option.
We also deprecate the --enable-logging option for rbt login, instead we'll

just use the --debug option to enable server logs.
These options now get set on RBClient as the web_login_options dict. It

makes sense to centralize these settings onto the client, so that callers can

easily set things in one place instead of having to plumb values through

various functions to reach the web login server. This will make more sense

in the context of the upcoming changes.

Used in upcoming changes.
Ran unit tests.
Tested using all versions of the web login, open browser, and

  debug/logging options and their .reviewboardrc config values

  on rbt login, rbt post and rbt status.