Add support to `rbtools` for command aliases.

Review Request #6491 — Created Oct. 22, 2014 and submitted — Latest diff uploaded

Information

RBTools
master
7816b0d...

Reviewers

rbtools aliases, which are defined in the .reviewboardrc file,
come in two forms: aliases for other rbtools commands and aliases
for system commands. The former allows for convenient short-hand for
rbt commands and the latter allows for more versatile and flexible
commands that utilize the shell. Aliases allow for positional variable
substition. rbtools aliases are only attempted to be executed after
attempting to find an internal command and external command (named
rbt-<commandname>) fail.

Add documentation for rbtools aliases. Add a link to the
documentation index to reference the documentation for rbtools
aliases.

Add unit tests to test the parameter substitution for rbtools
aliases.

Unit tests pass.