Fixing of useless message 'Unknown key : content' (read data)

Fixing of useless message 'Unknown key : content' (read data)

- After reading of data in RFC-8040 with set content query
  parameter, the INFO log with unknown query parameter was sent
  (but it was recognized correctly in another part of code).
- Refactoring of the readData(..) method, so the parsing of
  withDefaults query parameter is moved to ReadDataTransactionUtil
  that contains other parsing logic.
- Adding of withDefaults query paramameter to WriteParameters
  data class.
- Added unit tests.

Change-Id: I25a01c62a995facce24f29a0dc48048aa1e49f56
Signed-off-by: Jaroslav Tóth <jtoth@frinx.io>