Import the new dart:convert lib

A lot of important stuff is moved to this new library so we need to
import it.
There will be a lot commits after this which convert old code to use the
new features.
Converted network.dart to dart:convert

Changed the string encoder/decoder and how to compress things.

We still need to test the compress method and check if it can be done
better with the new API.
Import the new path lib

The name of the lib was before pathos but is changed to path.
Updated registernode.dart to new path style

Path's is now strings which is manipulated by using global methods from
the new path lib.
Updated request_bundle.dart to new path style
Updated download_request to new path style
Updated dart_import stuff to new path style

This should be the last thing to convert. Now we need to test it.
Forgot this one...
Small fix in logging
Fix path on Windows and check extension

The extension is now ".dart" and not "dart". One of many things there
are changed with the use of the new path lib.
Use the new concept of converter

By using converters we can simplify some code. Also changed Utf8 convert
and compressing to support the new converter concept.
Added debugging example to find communication bug

To find a fix for issue 3 we need a simple example there show the
problem.
Better logging message from sendportdb