Add public helper classes for UT mocking

Add public helper classes for UT mocking

Helper classes provide simple implementation for SDL public
APIs. These classes can be used in SDL clients as base
classes for SDL API mock implementations instead of deriving
mock implementations from pure virtual API classes. This way
mock implementations do not need to be changed every time
SDL APIs change (if the change does not affect UT cases).

Fixed also broken Doxygen include path and macro expansion.

Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: Idf62b1397b049b4f56b8ed90c57b53ed615cd67c