simplify CSP handling...All page's CSP rules are now removed when a payload is to be injected. When there is no payload, CSP rules are not modified but only supplemented with Hachette's own.
Facilitate installation of scripts from the repository...This commit includes:
* removal of page_info_server
* running of storage client in popup context
* extraction of some common CSS to a separate file
* extraction of scripts import view to a separate file
* addition of a facility to conveniently clone complex structures from DOM (in DOM_helpers.js)
* addition of hydrilla repo url to default settings
* other minor changes
and of course changes related to the actual installation of scripts from the repo