Improve the 'ftinspect' demo program

‘ftinspect’ is an essential part of FreeType to show how a font gets rendered by FreeType, allowing control over virtually all rendering parameters. The idea is to integrate each demo tools into ‘ftinspect’, based on the Qt GUI toolkit. Currently, it only provides the limited functionality of ‘ftgrid’. Thus, includes finishing ‘ftinspect’ handling all the aspects of ‘ftgrid’ and other demo tools.