Implemented multi-files.

Fix Exceptions (see issue #11).

Due to the fact that all java objects instantiate a FoldingDataEditorSupport.java, even when unopened or uneditable, we had a lot of exceptions.

This commit fixes those by deferring the instantiaton of a template provider until it is required and by checking if the file is writable.

Hide the toolbar when necessary.

The toolbar is now no longer visible on files that can not be templated.

We now have `.cookie` files to back up our application.
This means we no longer have in-memory files, file magic on close or need for the MainCloser.java.

It simplifies the code a lot.
Merge pull request #13 from jjpe/multifiles

Implemented multi-files.