More renames of files and tools moved into own directory
Refactored classes and API names

- main class is now just zyre_t
- two ZRE message classes also exported to API
- all other classes' header files are in src
- class names are now easier to understand
- removed java tree, which is forked off to jyre project
Fixed some issues with last changes

- extended test cases
- upgraded to use latest CZMQ master
Merge pull request #112 from hintjens/master

Refactoring Zyre (still in progress)