Circle highlight improvements

[Robert Leach]

I have pretty much already implemented these things. Just wanted to document it a bit in bitbucket.

1. Draw a circle based on pixel size of the selection instead of only when a single cell is selected.
2. Draw more than one circle if there are more than 1 small selection
3. Do not draw a circle if a small selection is near another selection
4. All selection circles yellow and all viewport circles white

As a demonstration of item 3, here is a screen capture where I prevented the drawing of circles when another selection is nearby. Note, the case of a first selection being near to the next was a special case and as you can see here in this screen shot, it works. The nearness improvement in the screen show is in effect for the interactive matrix and not for the overview. Note hot the top left selection is circled in the overview and not in the main view. Also, I tested when small selections are far apart and the circles DO appear in those instances.

[Robert Leach]

Fairly straightforward changes.

[Robert Leach]

Merged to master.

[Robert Leach]

Removing milestone: General interface (automated comment)