1) force version pinnings 2) add sane pinnings suited for plone 4.3

Trying to install a plone site (no addons) and a plone site with PAM from the current buildout failed for me.
I ran into the ['portlets.Events' bug](https://dev.plone.org/ticket/13935) and into the recently reported issue [plone.app.multilingual 2.0a2 can not be installed](http://plone.293351.n2.nabble.com/plone-app-multilingual-2-0a2-can-not-be-installed-td7570879.html)
Also, buildout had pulled in too new version of p.a.event and p.a.c. Therefore I completely disallowed picked versions (I hate surprise updates, even in a dev environemnt...) and added various version pinnings. To avoid those 2 bugs linked above, we need to include both p.a.c and p.a.e as eggs in the instance.

With this setup I can again create a Plone site (no addons), and also a site with the PAM profile, as long as  the "Dexterity-based Plone Default Types" (p.a.c) profile is included at the same time.

If you agree, please merge