Check ModelTypes in jacorb subsystem

There are a number of attributes in the Jacorb subsystem that use ModelType.STRING for things that look like booleans. Check through the attributes and change to ModelType.BOOLEAN where appropriate.

This shouldn't raise a compatibility issue, since ModelType.BOOLEAN is freely convertible to ModelType.STRING, and vice-versa so long as the string represents as boolean (which it would have to do for the attribute to work anyway.) If anything is changed though, a Console subtask should be created to look into any UI implications.