Enabling local frameworks

* Users can now provide their own local frameworks, by using either
  UDTC_FRAMEWORKS=/path/to/directory and dropping those frameworks here,
  or in ~/.udtc/frameworks/. Fixes #29
* Duplicated categories and frameworks loading order is the following:
  1. UDTC_FRAMEWORKS content
  2. ~/.udtc/frameworks/ content
  3. system ones.
* Note that duplicate filenames aren't encouraged, but supported.
* This will help as well testing for large tests with a basic framework for
  all the install, reinstall, remove and other cases common in all
  baseinstaller frameworks
Add README for this new framework loading mode
Add tests for the framework local loading

* Add assets and small tests for ensuring we can load local frameworks.
* Small cleanup in unecessary teardown