Handle time and tree for configurations & mount/unmount actions

This MR switches from the configuration hierarchy to the usage of mount & unmount actions. The usage of those actions, together with a selection of the date define the shape of the configuration tree.

There are also new forms to insert the mount & unmount informations (contact, offsets, descriptions) - and a new tab to show the list of mounts & unmounts (a page that later may also be used for actions of the devices & platforms).