Support shared, device-specific i3 configurations

Separated i3/configuration since some of my devices support XFree86 keysyms
while others do not. This introduced some cascading changes.

- Removed ~/.config/i3/config from this repo. Since I will be switching between
  devices semi-regularly and that file will be generated each time I switch to a
  different device running an X session, I don't want the i3/config to spam my
  `gst` and `gd` when I haven't changed configuration in either config.shared or
  config.device.
- Update aliases, variables, etc. to point to config.shared instead of the
  generated file.
- Ensure that X sessions generate the i3/config file.
- Ensure that i3 reload and restart command generate the i3/config file.

configs/shared/x_server/.xsessionrc.shared

@@ -23,5 +23,10 @@ emacs --daemon
 xmodmap -e 'remove Lock = Caps_Lock'
 xmodmap -e 'keysym Caps_Lock = Escape'
 
+# since we separated our i3 configurations between a shared and device-specific
+# setup, we need to make sure that when we start an X session, our i3
+# configuration is up-to-date.
+cat ~/.config/i3/config.{shared,device} >~/.config/i3/config
+
 # set key repeat preferences
 xset r rate 250 60