Added code to generate the full path to the image preview

The image entity can't generate the full path as it doesn't know the location of the web directory.
Added tests for ConfigureEvent, ConfigureQueryEvent and PersistenceEvent
slovenian translations updated
Admin minor CS fixes
Add blocks before and after main navigation

This commit adds two blocks before and after main navigation.

I will use this to add :

- locale switcher for admin
- store switcher
.....
Apply select2 on appended form element
Allow to use translation_domain in FormMapper fieldDescriptionOptions

This will call this function https://github.com/sonata-project/SonataAdminBundle/blob/master/Admin/BaseFieldDescription.php#L466, so it works even if translation_domain is not specified.
Add body_attributes block

This allow us to customize login screen
+ change admin design based on user for company which have different brands
Updated italian translation
Add German translations for global admin search
Update SonataAdminBundle.pl.xliff
fix indentation for repeated fields and others
Update base.js

Problem occured during my dev
Update jQuery form plugin to v3.45.0

Fix #868
Fix #1729
Restore IE workaround 

https://github.com/sonata-project/SonataAdminBundle/pull/1797#issuecomment-28623826
Added tests for Admin methods: getRoot, getRootCode, setPersistFilters, getExportFields
Added test for historyViewRevisionAction
Added tests for batchAction In CRUDController
SonataAdminBundle translation to Lithuanian language
Minor CS fix in CRUDController