Add the ability to manually select a command-line method

[david-christiansen]

In some cases, the existing command-line selectors in the alist are sufficient, but the order is incorrect for a particular project. For instance, a project's repository might have build files for Nix, Stack, and cabal-install, and a user may have a reason to prefer one of those over the others. This change allows a setting in .dir-locals.el to override the order of the command-line method alist.

[jyp]

I don't think that I understand your rationale very well. Why don't you override directly dante-repl-command-line ?

[david-christiansen]

The built-in command line methods run some Lisp to compute a command line, which can be more convenient (and potentially more maintainable long-term as build methods get updated) than figuring out what the command line is supposed to be by hand.

[jyp]

I've done something which I believe is cleaner in fd07920 Let me know if I missed something.

[david-christiansen]

fd07920 looks great. Thanks!