More debug traces for tracking issues with new leiningen launcher, etc.
feat(plugins): Support for user plugins in $HOME/.ccw

Arbitrary contributions to the Eclipse 4 Model can be made, or
modifications to ccw vars.

- every folder under $HOME/.ccw containing 1+ clj file is a plugin folder
- the plugin folder is added as a classfolder in CCW's classpath ...
- ... while each clj file at the root of the plugin folder is loaded
  (no guarantee on the order)
- contributions to the Eclipse 4 Model can be made via the ccw.e4.dsl
  macros
- any contribution provided by a previous load of the plugin that is not
  reinstalled during the plugin load is automatically removed from the
  model (only works for Commands and Handlers ATM)