Added UI (X incl. xfce) and Eclipse installation

Hi,

here's a suggestion to add GUI and Eclipse installation to the VM build.
just started last week to work hands-on with packer, puppet etc. - so please forgive me if things are not as elaborate as they could be.

Changes in this set:
---
Added GUI - X incl. xfce - and Eclipse installation (site.pp,
packages.pp, new eclipse.pp)
Packer JSON file modified:
- a workaround to set the hostname correctly (did not work on my
machine at least / OS X 10.9.1, virtual box 4.3.6; it stayed at
„localhost“, making the build fail as the node name could not be
matched afterwards)
- an addition to the puppet execute_command (install archive module)
- increasing RAM and (for GUI) VRAM for
---

Discussion:
Not sure whether the hostname workaround should be pulled actually. Martijn already confirmed it works on his machine, and he is on OS X Maverick as well.
An alternative to the manual installation of the archive module could be to use librarian_puppet I had looked into it and thought it was overkill however (maybe that changes as we add more stuff)
There seems to be a ready module to install IntelliJ IDEA (smarchive/idea), but I assume that Eclipse is more widespread, so I started with it. 

Cheers,
Andreas