Generalize new workspace addition functions to support arbitrary insertion.
Generalize new workspace addition functions to support arbitrary insertion.


The current DynamicWorkspaces module only supports adding new workspaces
at the start of the list of workspaces. This means when binding workspaces
to keys based on the position in the list, key bindings can change 
as workspaces are added in removed in a far more destructive way than
necessary. Instead, supporting appending and arbitrary insertion allows
the user to determine where the new workspace should be added.

This patch is a straight generalization of the addHiddenWorkspace' function.
Rather than always using `(:)` to insert the new workspace into the list
of workspaces, this patches causes it to use an arbitrary list insertion
function instead. A few new functions are added to prevent breakage of
external code while exported functions are left unchanged.

List of new functions:
  appendWorkspace
  appendWorkspacePrompt
  addWorkspaceAt
  addHiddenWorkspaceAt

Existing functions were modified to call their generalized brethren where possible
without changing functionality. This patch should not change behavior for any
existing users of this module.


CaptainPatate/xmonad-contrib,f1u77y/xmonad-contrib,mathstuf/xmonad-contrib,xmonad/xmonad-contrib,ohlus/xmonad-contrib,ohlus/xmonad-contrib,CaptainPatate/xmonad-contrib,mathstuf/xmonad-contrib,ohlus/xmonad-contrib,0/xmonad-contrib,mathstuf/xmonad-contrib,0/xmonad-contrib,pjones/xmonad-test,f1u77y/xmonad-contrib,CaptainPatate/xmonad-contrib,xmonad/xmonad-contrib,0/xmonad-contrib