make public method for getting a reference to writing executor so other classes can monitor image writing

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14414 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
Fix Exposure field for locales using comma as decimal point

Fix bug introduced in r14402.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14415 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd