Repo library metadata

Added support for library metadata. Now repo also keeps a library.json and library.png files at the same level of the main library.zip file with the resources. These metadata are now retrieved from mockup, but only the name is used. View still needs to be redesigned to display some of the data available (1) thumbnail  - also needs downloading; (2) size in mb; (3) description; (4) author summary; (5) license summary; (6) number of elements