concerning unittest & field validators

Fixes problems with plugins

- updated scripts etc
- make tests pass

- Replaced some "hidden" import with LodelContext.expose_modules calls
 - in some functions of Setting, Plugin, validator
 - in loader.py (temporary version)

In this state the tests runs (151 success), I'm able to run an instance (from debian package using slim) in MONOSITE mode and in MULTISITE mode by creating and loading a context in the loader.

Add master = true to uwsgi.ini

Add the possibility to give a fixed name to instances created by mass_deploy

mass_deploy now warns you when using $RANDOM instead of pwgen or /usr/share/dict/words

with make deb . Next commit will update the README

Now mass_deploy is able to stop when slim fails indicating on wich action slim fails
Bufixing webui conf edition

broken nginx conf + absolute path in slim that is known only at build time

Remove duplicate install templates directories (the same directories can be used by SLIM & runtest)
Addapted runtest so it can fetch the install template from the lodel2 datadir
Make lodel_admin.py runnable (add the python3 shebang + chmod +x at install-data target)
And a beautifull ASCII formating for the README

Allow to remove all database prefixed by MONGODB_DB_PREFIX (in the conf of mass_deploy script)

Allow generating a tarball that can compile and run lodel2 + deletion of unwanted Makefile.in files

Forgotten file was the PID list file
The bugfix concerns the conf when selection mongodb as datasource (quick & dirty solution : keep dummmy_datasource loaded so we don't have to modify the original datasource conf)

https://docs.mongodb.com/v2.4/reference/user-privileges/
https://docs.mongodb.com/v2.4/reference/privilege-documents/