Add Admin Dashboard

This rather huge, unsquashed patchset adds an Admin Dashboard (`Admin`) in Synnefo. Admin is the Synnefo component that provides to trusted users the ability to manage and view various different Synnefo entities such as users, VMs, projects etc. Additionally, it automatically generates charts and statistics using data from the Astakos/Cyclades stats. Admin is a top-level Synnefo app that resides in the `snf-admin-app` folder.

Before testing it, it needs a change in the `debian-release-0.16` branch, which will be uploaded soon.

Also, note that there are a few commits that update files out of the `snf-admin-app` folder. It's probably useless writing here their SHA , since that may change, but an easy way to identify them is to check the logs for commits starting with `ci: `, `deploy: ` and `common: `.