Add support to set cmd, change keybindings, change installation directory and fixed various errors

First, sorry for making this one PR (I should have divided it into little ones, sorry)

This just add support for "cmd" in config file, and changes the makefile to select installation directory (/usr/local or ~/.local for example).

It also fixed some XML issues (not sure that they are important), and tries to improves some things (fmt, log...)

Sorry if you don't need this, just try to help