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/zsh/aliases.zsh

@@ -142,7 +142,7 @@ alias ea='e ~/aliases.zsh'
 alias ef='e ~/functions.zsh'
 alias el='e ~/variables.zsh'
 alias ex='e ~/.Xresources'
-alias ei='e ~/.config/i3/config'
+alias ei='e ~/.config/i3/config.shared'
 alias em='e ~/.tmux.conf'
 
 # couple the s* aliases to the <leader>s* kbds in vim

configs/shared/zsh/variables.zsh

@@ -48,4 +48,4 @@ a="$HOME/aliases.zsh"
 f="$HOME/functions.zsh"
 l="$HOME/variables.zsh" # v is taken by vim
 x="$HOME/.Xresources"
-i="$HOME/.config/i3/config"
+i="$HOME/.config/i3/config.shared"