Exclude nodeTypes from being stored / exported per form

[Benjamin-K]

PR #25 added the option to exclude some nodeTypes from storage / export. The next step would be to exclude some fields only for a specific form.

Steps to be done:

• Add option to the Finisher for excluded nodeTypes in storage.
• Add option to the Finisher for excluded nodeTypes in export (is this possible?)
• Add option to single items to be excluded from storage / export (node based form only?)