Fixes to the plot view UI: will make the UI conform to PlotUI.txt

-Make the mouse target area ~20% (5 pixels) of the size of the mouse marker.
 The mouse will be pointing at the highest view object which is anywhere 
 inside the target area, to make it easier to select thin items, like thin
 lines.

-Make it so that in layout mode, the mouse can select any view item, including
 child items.

-Make it so that a selected view object, including child items, can be dropped
 anywhere in the current window.

-Make it so that on drop, a viewobject will become the child of the highest
 viewobject which fully contains it (could be the top level view).

-Change text mode as follows:
	-Add a Scalar Selection Combo box to the text dialog
	-Change the order to: 
		-Scalar list combo, Text, font, font size, 
		 Resize label for text, H Justification,
		 V Justification, data precision, Rotation,
		 Transparent fill, Font colour, box properties
	-on opening a text edit dialog, give focus to the text entry
	-Set the icon to the text '|' icon.
	-On single click open the text edit dialog with the following settings:
		-Transparent fill selected
		-Resize for label selected
		-Horizontal Justification Left
		-Vertical Justification Center
		-Border width 0
	 On OK, the label will be inserted at the click location.
	-On a drag behave as it currently does (turn the mouse icon to the arrow during
	 the drag), except change the label dialog defaults to:
		-Transparent fill not selected 
		-Resize for label not selected
		-Horizontal Justification Center
		-Vertical Justification Center
		-Border width 2
	 At the end of the drag, insert the label in the box.

-View objects which are children of 2dplots need to be positioned relative to the
 axis box, not relative to the whole kst2dplot, so that if, eg, the axis label font
 size is changed (changing the border with) the child view object will stay fixed 
 relative to the axis (imagine an arrow pointing to a feature).

