Preparation for Issue #90 and license checking

This pull request contains a simple script to check that all licenses within the project look the same. I would like to discuss the script and create a external plugin for license / text file header checking afterwards.

All project python source files (including tests, except build.py and check_licenses.py) have the same file encoding comment and license header now.

I created simple tests for the plugins PyFix, PyMetrics, PyLint, Pep8.
This script is just a "sketch". I would not want to use the docstring either. I want to create a plugin a set a property on the plugin which contains the license string.

something like ...
```python
use_plugin('pypi:pybuilder_license_plugin')

@init
def init(project):
    project.set_property('license_text', """This is the license text

Hello world
""")
```