remove old resources during merge to prevent transfer of fields (the possible order change causes e.g. non-uploaded resources to become uploaded

- sometimes the session got lost (e.g. if you renamed the cookies and
probably if servers were switched or restarted) and authtkt_identity was
then None, so checking of drupal session prefix was not always possible

Users can like datasets. When pressing button in GUI a cookie with
package id is set and number of likes is increased if the user does
not have a cookie with package id.
A separated table for package likes is created to avoid updating the
whole dataset.

Fixes buttons and listeners after changing package type.
Disables saving url resources with different package type.

Fixes uploading files and adding files with URL.
Fixes copying of unsaved data on changing package type.
Adds listener for data change after posting package resource.
Unifies text on buttons for checking links.

And sets table column width before showing success or
error message to prevent jumping content.