functions: optimization: get the DOI for a file -> avoid unecessary web requests.
Adding function unLike to unlike a post.

hosts: adding function getDoi, to get the DOI for a file. Also, now the
parsing of the data returns the origin url of a post.

know.py: adding preferences: can restore window state.
Adding images for the actions.
Adding action to calculate percentage match.
Adding actions to like and unlike a post.
Adding action to open a post in browser.
Getting the data is a bit more stable. Updatibg the view is done by the
user in the main window, manually, and it doesn't suit me. Some work has
to be done.