Experiment design view improvements.

The experiment design view has been improved with the following
modifications:
	- Tree rows are highlighted with the associated condition color.
	- Replicate placement now works correctly. Replicates can be selected
in the tree or in the spreadsheet, and then they can be placed.
	- A selected replicate can replace another placed replicate holding
"Ctrl".
	- Spreadsheet grabs focus when a item is selected in the tree.
	- Color schemes and manipulation has been improved. Class ColorUtils
contains several color utilities.
	- Entities have been modified for a better replicate placement support.
	- Tree now shows when a replicate is placed.