Started new dotfiles management tool.

Created an argument parser to lay out the main functionality for the
program.
Added detail to argument parser options.
Added functionality to pass 0, 1 or more files to the commands.

The files are specified by name only, and the system then calculates the
full paths to each file (using the directory that the script is in as
the assumed dotfiles repository).

If 0 files are passed, all valid dotfiles in the repo are used as a
default value. This also ignores all files specified in the .gitignore
and in the IGNORED_FILES list at the top of the script.
Refactored code and added placeholder methods for main functionality.
Fixed file arguments passed to the add command.
Added the linking functionality (along with some helper functions).
Added list functionality, including with optional --unlinked argument.
Added check to `add` command to ensure file(s) are in the repository.
Added dotfiles alias to .aliases
`list` now checks to see where a link points

Before, the `list` command would just check to see if there was a symbolic link in the user's home directory with the same name as a file in the dot files repo. Whilst this will usually work, it can't be relied upon.

The `list` command will now check to see if there is an appropriate link in the home directory, as before, but will now also check to ensure the link points at the corresponding file in the dot files repo.
Fixed the file error checking in the `add` command.
Added `edit` functionality.
Tweaked comments/documentation.
Added 'add' functionality.
Got rid of 'remove' functionality - when will I ever want this?

The 'remove' functionality can be performed with a simple rm terminal
command, it's not necessary to write a script for it.
Added checkout alias to .gitconfig
Mostly rewrote the dotfiles script (again), this time folders work!
Added the other functions to the dotfiles script. It works! :D
Removed the old outdated versions of the install script.
Merged the much better versions of the script into master.