Changed read to be type-safe in ReadTransaction

Changed read to be type-safe in ReadTransaction

Removed declaration of read method from common
superinterface, which is now only marker interface
for read capabilities.

Defined read method in specialization of interface
for Binding and DOM interfaces, which makes
use of specific features of format.

This change is source-code compatible
and users of read method needs to update
their code appropriatelly as shown in
Toaster example.

Change-Id: I8c783fc5f276722a5a762eea7c769c3f54a31855
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>