Basic, initial  implementation of graphs

This is more a proof of concept, although a working one, but still unpolished.
In this pull request you may find a new Graphs tab in the console and two predefined graphs (and tables).
One graph outlines the variability in versions for each product in the live model and another outlines variability in versions per product in the desired model, they are very similar.
Both graphs should be fully functional under the assumption that metadata.product exists for each entry and metadata.version is an integer. If they don't exist (or not an int) then it simply fails gracefully.
To continue this work, after this initial review, I have a few more ideas of predefined graphs that can be useful plus finding a way to make graphs definitions completely generic by letting users define the metrics to be graphed in the config file (currently it's a list of two predefined graphs that a user can choose whether to include them or not).
So the work isn't done, however I'd appreciate a review to tell me whether I'm generally in the right path and you may pull or not pull depending on your policy - the version had not been battle tested, but there are no current known issues. 
Yan, I know you're on vacation, so really no need to hurry up, it's cool, I'm not blocked...