Bouncycastle was added to the project
Some refactoring was done
Bouncycastle was added to the project. Again.
Redundant dependencies were removed from bouncycastle
<input type="file"> was remove iframe uploading was added instead

See http://jenkins.361315.n4.nabble.com/Config-Form-File-upload-problem-td2993433.html for some more details.
As we can not use <input type="file"> in config.jelly, it was decided to put file upload form into an iframe and,
once it's uploaded, put Base64 encoded file content to a corresponding <input type="hidden">