Add a correct configuration for the Metatags

[jorgegalindocruces]

There are a few Metatags (For example the Twitter one) that don't show the information and the picture of the website correctly.

I think that the problem is in the poster.jpg, that variable has to be optional into the SBT configuration. We can check if other meta tags are correctly configurated as well (for example Facebook) and add other like Meta Keywords.