Remove Debian packaging

Packaging will be moved to the Debian Python Applications Packaging Team
(PAPT) repository.
Fix setuptools entry point invocation

Reported by Emmanuel Blot, fixes 24e191f.
Fix missing import
Move static files to webcheck/static

This moves all static files to be installed into the webcheck Python
path and uses pkg_resources to load the files.
Fix setup.py script

This makes the script executable, adds copyright headers and ensures
that all needed files are installed and shipped in the source package.
Only convert content if link has encoding

This fixes an issue for calling tidy when the character encoding of the
page could not be determined.
Store link and page problems as unicode

This converts problems to unicode so they can be stored correctly by
SQLAlchemy. This amongst other things fixes a problem when the web
server returns a status message with non-ASCII characters.