Change container of index

Drop ExactMatch since nobody uses it and it operates directly on the
index
See details:

 * Make search a composite member instead of an inherited index class
 * [APPINDEX] Save icon instead of doing lookup every query
 * [APPINDEX] Keep track of installed apps
 * [APPINDEX] Show index build info via signals
 * Completely drop the indexservice from design
 * FileFinder is broken
Remove restoreDefaults from Service interface
Replace errorprone SIGNAL/SLOT makros by member-funtion-pointers
Localize the calculator