Added Auto ID Behavior for Dexterity Contents

[ramonski]

Description of the issue/feature this PR addresses

This PR introduces a Plone Behavior to generate IDs for Dexterity based contents.

Usage

Add this XML into your Dexterity profiles/default/types/<Content>.xml:

  <!-- Dexterity behaviours for this type -->
  <property name="behaviors">
    <element value="bika.lims.interfaces.IAutoGenerateID"/>
    ...
  </property>

Current behavior before PR

Dexterity contents not integrated into the ID Server machinery

Desired behavior after PR is merged

Dexterity contents supported by the ID Server machinery

--
I confirm I have tested this PR thoroughly and coded it according to PEP8
and Plone's Python styleguide standards.