Refactoring: rm p4a, support for dexterity

this branch is quite a big refactoring with the goal of removing the p4a.subtyper and adding dexterity support (which was not available because of p4a.subtyper's folderish descriptor).

Please note, there is no upgrade step. currently you have to 1) remove collective.lineage in the 1.x branch, 2) remove p4a.subtyper in quick installer, 3) upgrade the codebase to 2.x branch, 4) reinstall collective.lineage.

Changes include:
- Content type framework agnostic: Compatible with Dexterity and Archetypes by allowing definitions of Subsites on plone.folder.interfaces.IFolder objects.
- Remove dependency on p4a.subtyper. Enable and disable subsite menus are now in the object_buttons action menu.
- Remove controlpanel. Use language translations for translating interface elements instead.
- Remove upgrade steps and migration for 1.x based versions. Please migrate your site to the latest 1.x version before using 2.0.
- Remove deprecated ChildFolder content type.
- Remove upgrade steps. Please upgrade to most recent 1.x version in the 1.x branch, deinstall collective.lineage and use the 2.x branch then nad reinstall. Please make a list of all your subsites before, as you have to re-enable them manually. There is no upgrade step for this yet.