JAV-324 Deprecate encrypted transfers

[Radiokot]

Purpose

Deprecate encrypted transfers. They are deprecated and partially removed since protocol version 7.

Changes

• Add deprecation annotations and Javadoc notices to builders, factory methods and classes associated with encrypted transfers

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.