Make more Autobahn tests pass

A couple of fixes and refactoring to make QtWebsocket pass more tests from the Autobahn test suite.

#### Changes
* Make tasks to run tests
* Refactor frame composition
* Refactor `::processDataV4` to use new class `QWsFrame`
* Fix ping handling
* Various other fixes
* Doxygen documentation

#### Todo
- [ ] Fix compilation errors for examples