Added display of mount actions in platform actions timeline

Closes #108 (closed)

This MR adds the display of platform mount and unmount actions in the platform > actions tab.

It includes only those actions that affect the selected platform directly - it does not show when other platforms or devices were mounted on the selected platform (so where the selected platform is the parent platform). The reason for that is that we are able to list the mount actions in our data model but not the related unmount actions, as those doesn't have a link to the parent platform anymore.