rewrote the logtrail core according to new specs

- replaced config/default.json with config/default.js
- commented examples/simple.js until the core is functional & tested
- replaced lib/formatters/* with a single format submodule
- wrote tests for the format submodule
- wrote a modified (improved) logger function
- removed the test for old logtrail core (which would fail with the new one)

TODO:
- add capability: write to files (strip colors)
- add capability: set loglevel without reconfiguring
- add capability: extend log types
- write test: logtrail core