each common library that requires the classloader now inherits from it explicitly, this removes the requirement on an individual module to inherit from a mixin that they do not explicitly use
updating various modules that were explicitly importing the ClassLoader and causing a weird MRO error
adding a dictionary of variables, and performing inline substitution of these with various commands before they are executed; refs #75
implement three new shell commands: set, unset and echo to manage variables and to view what will be executed once a command has been pre-processed; refs #75
set some initial variables in the drozer shell,  (maps to the expected working directory) and /home/dbradberry/bin:/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/share/android/ndk:/usr/local/share/android/sdk/platform-tools:/usr/local/share/android/sdk/tools:/home/dbradberry/.rvm/bin:/home/dbradberry/Documents/projects/mercury/workspace/mercury/bin (the system path, including our bin folder); refs #75