Don't resolve when the first character of the command starts with a dot.

Refs #52.

It's not a `\' like shell alias management cause, the shell replace:

- dctc \ls

by

- dctc ls

We need to write `dctc \\ls' if we set the escape character to `\'.

* src/dctc/java/com/dataiku/dctc/configuration/Alias.java: Here.