Provide a Develop sub-menu to change the default logging level

It would be convenient when examining problems to be able to directly adjust the default logging for the viewer.

This issue tracks providing a Develop sub-menu to set the default logging level. Changes made through the menu should be equivalent to changing the "default-level" key in logcontrol.xml. The logging system should use whichever value (the one specified on logcontrol.xml or the one set by the menu) was changed most recently.

The menu should not make a persistent change - it should not modify logcontrol.xml or make any other change that survives the current viewer session.