Bump development version to 1.4.20

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14583 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
ASITiger: initial PLogic device support, various minor cleanup

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14584 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
MultiChannelShading plugin: start of tabgle model

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14585 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
ASITiger: for PLogic added IOType, other minor fixes

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14586 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd