Added support for XEP-0141: Data Forms Layout.

Data Forms layouts are a part of Data Forms and implemented as extensions, added to a Dataform.
Support for XEP-0141: Data Forms Layout.

Data Forms layouts are a part of Data Forms and implemented as
extensions, added to a Dataform. Fixes issue SMACK-612.
Support for XEP-0141: Data Forms Layout.

Data Forms layouts are a part of Data Forms and implemented as
extensions, added to a Dataform. Fixes issue SMACK-612.