Bug 489919

Right now, Baloo indexes only file names (and contents of files), which are not excluded via the file type list in

```
 ~/.config/baloofilerc
[General]
dbVersion=2
exclude filters=*~,*.part,*.o,*.la,*.lo,*.loT,*.moc,moc_*.cpp,qrc_*.cpp,ui_*.h,cmake_install.cmake,CMakeCache.txt,CTestTestfile.cmake,libtool,config.status,confdefs.h,autom4te,conftest,confstat,Makefile.am,*.gcode,.ninja_deps,.ninja_log,build.ninja,*.csproj,*.m4,*.rej,*.gmo,*.pc,*.omf,*.aux,*.tmp,*.po,*.vm*,*.nvram,*.rcore,*.swp,*.swap,lzo,litmain.sh,*.orig,.histfile.*,.xsession-errors*,*.map,*.so,*.a,*.db,*.qrc,*.ini,*.init,*.img,*.vdi,*.vbox*,vbox.log,*.qcow2,*.vmdk,*.vhd,*.vhdx,*.sql,*.sql.gz,*.ytdl,*.class,*.pyc,*.pyo,*.elc,*.qmlc,*.jsc,*.fastq,*.fq,*.gb,*.fasta,*.fna,*.gbff,*.faa,po,CVS,.svn,.git,_darcs,.bzr,.hg,CMakeFiles,CMakeTmp,CMakeTmpQmake,.moc,.obj,.pch,.uic,.npm,.yarn,.yarn-cache,__pycache__,node_modules,node_packages,nbproject,core-dumps,lost+found
exclude filters version=8
```

Meaning, if you try to find an existing file, called e.g. `abc.vdi`, Baloo will tell you that it can't find it:
```
baloosearch -i filename:abc.vdi
```

From a UX POV it would be much better if Baloo indexed file names of any files, but just excluded the content of file types from the list above.