[dev oct 11] Sometimes File | Mount Filesystem... just beeps and does
nothing, as when e.g. no nodes are selected. It should always be
turned on. The code appears wrong; it is extending NewTemplateAction
which is a NodeAction, which will enable/disable itself acc. to
current node selection. NewFileSystemAction sets itself enabled in the
constructor (note: this is wrong, initialize() is meant), but this is
useless since it may be turned off later. I suggest: only one of
NewFileSystemAction and MountAction should exist with any real code,
the other extending the first but not overriding any methods; and they
should extend CallableSystemAction directly rather than
NewTemplateAction.