Fix rounding of displayed float values

For example, 0.00005 was being "rounded" to 0, instead of 0.0001.
Regression test added.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14604 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Remove incorrect comment

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14605 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd