some more initializers in some headers, and qt 4.6/4.7 compatibility backguard

* ...in previusly commits, so fixed #4 property (still more in filename handler) in NBAppFile.hpp
* some more initializers in some headers, and qt 4.6/4.7 compatibility backguard in NBMimeDatabase.cpp
* temporally workaround for qt 4.6/4.7 compat in locale lister for NBMimeType.cpp