Moved c4dtools.helpers.Importer to c4dtools.utils

- Extended description of c4dtools.utils.vmin(), ~.vmax(), ~.vbbmid().
- Added c4dtools.utils.current_state_to_object() and ~.clsname().
- Added docstrings for c4dtools.utils.Watch class.
- Changed docstrings of c4dtools.utils.FileChangedChecker class.
- Added c4dtools.utils.Filename class.
Extended functionality of GraphNode class.

The c4dtools.misc.graphnode.GraphNode class now has more options to
change the visuals of a node in the XPresso Editor. This includes:

- Position of the view-camera (GraphNode.view_position)
- Zoom-value (GraphNode.zoom)
- Type of view (GraphNode.view)
- Fixed behavior of node-sizing (differed for XGroups in Extended View
mode)

TODO:
Changing the GraphNode.view to GraphNode.VIEW_FULLSCREEN does not make
the node fullscreen. However, the value of VIEW_FULLSCREEN has been
proven to be 3.
minor changes
Revert "Moved c4dtools.helpers.Importer to c4dtools.utils"

This reverts commit 7640f99bb5d58b7cc3ff62bd565bff9d284d14a3.