added a default value for Subsection parent field

adds a default value to Publication collection field

**kwargs was not given to super() constructor

Implements a new exception class for webui : HttpErrors that uses a new template : errors.html to display multiples errors

Before we were calling the logging.getLogger function without argument. The result was
that all contexts were sharing the same logger (and every message were logged X time with
X the number of loaded context).
Now getLogger is called with the context id as argument, each context has its own logger.

WARNING : not fully tested

Now the loader context is threated like the others (it loads it's libs from a symlink, before it was loading them from lodel package)

a bit dirty & quick

They were a bug when ordering stuff contains 2 values that are equals

was disabled for debugging...

Previous bugfix on runtest & create instance brokes deployment, now both seems to work fine

- a "normal" import was left in lefactory_common
- the hook triggering datasources init in dyncode was not called
- dyncode was not exposed in the loader (making hook call useless : the hook has to be called once the dyncode has been "seen" (imported) by python)

lodelsites was created inside the lodel directory

Regression may have been introduced about MONOSITE mode

concerning unittest & field validators

Fixes problems with plugins

Conflicts:
	lodel/plugins/multisite/loader.py

+ uses the changes in the preload method

- found a way to make it implements the socketserver.ForkinTCPServer features reducing the global code size (and removed a lot of dirty copy & paste from cpython sources)
- deleted useless imports