To avoid build conflicts with Qt5, with this patch, 'qt4_deprecated' needs
to be added to the 'SPECS' variable (in specs.conf) when building for Qt4.
Issue #345.
- Remove example application source code files which also exist in contrib
- Outsource commonly used parts from target.mk files
- Store the current Qt version only in one place
- Add run scripts for the example applications
Fixes#127.