Rudimentary crash prevention: Check plugin compatibility before load attempt

Due to memory ordering compiler optimizations, the exported *gloperate::Plugin* in release mode does not necessarily correspond the debug version (and vice versa) of *gloperate::Plugin* - thus causing memory violation when loaded by the *PluginManager* after all.

The bug can be reproduced by installing debug & release versions into the same folder by executing the **viewer-qt** application (tested with MSVC12, but should occur with gcc/clang aswell in high optimization levels). The fix does only check compatibility by debug indicator in the library's filename. A more sophisticated solution might be useful.