QtTest: Output correct library name

"QTest" is the C++ namespace; "QtTest" is the library name

- Edited the logger output in qplaintestlogger.cpp
- Updated documentation
- Updated expected outputs for self-tests

Change-Id: I43c525c43221a8d4e843a00d6d55b0f06ef55fd7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>