This removes ArgMatches from the Context struct and replaces it with a simple HashMap. This work is towards getting Starship in a better place for use as a library in other shells written in Rust so they don't need to use a command-line interface to invoke and configure things.
Contributes to #521
A couple of optimizations are done in this PR. One, we now will check config ahead of time to see if a module is disabled before running any module code. Also, we won't try to discover a git repository unless the module requests access to it.
Implement a timer module that takes a commandline argument, the number of seconds the last job took to complete, and displays it if appropriate.
Alters shell initialization files to compute this number using date +%s where needed.
Adds a config section to configure minimum amount of time before timer is shown (default is 2s)
