Update sml path and user config
Add C-l shortcut to clear nrepl and geiser mode repl
Add shortcuts to start, close and restart sml repl
Minor fix.
Update sml load file and load test file in sml repl, more robust.

To load a file and run sml repl -> Press C-c C-v inside a sml file.
To run the current files tests -> Press C-c C-r inside a sml file. It
assumes the tests are inside the same directory. For example, If your code file is hw1.sml your test file should be named as hw1tests.sml in the same directory