PSR2 build

Update develop with latest commits in master

Fix example 5.2.

[Ready] PSR-2 compliant

Typehint alias consistency

Fixing type hints on Document that should hint on DocumentInterface

Conflicts:
	library/Solarium/QueryType/Analysis/Query/Document.php

Example of "add" with optional update attribute to set a field to null (i.e. delete a field):

<add>
  <doc>
    <field name="employeeId">05991</field>
    <field name="skills" update="set" null="true" />
  </doc>
</add>