i3: add xinitrc file

 * Add xinitrc file to start i3 window manager
 * Move startup applications from i3 config file to xinitrc
i3: change keybindings

 * use mod+q and l instead of mod+l for lock
 * use mod+q and e instead of mod+shift+e for exit
 * use mod+z instead of mod+c for child container focusing
 * disable keys j,k,l,; in resize mode
i3: change default terminal and programs menu

 * use xterm by default
 * use dmenu instead of i3-dmenu
i3: change position of the status bar

Move status bar to the bottom of the screen