Add filtering of numerical cols to collection

CollectionFilterWidget: Updated the tooltip, to reflect the changes.
CollectionQuery: Add parsing for SQL operators and insert right SQL
"where" searches.
Song: Add list of numerical columns
playlistfilterparser.cpp/FilterParser: move time and rating parsing
functions to new file:
searchparserutils.cpp: Contains common code used to parse search terms
in playlist and collection filters.

src/CMakeLists.txt

@@ -57,6 +57,7 @@ set(SOURCES
   utilities/filemanagerutils.cpp
   utilities/coverutils.cpp
   utilities/screenutils.cpp
+  utilities/searchparserutils.cpp
 
   engine/enginebase.cpp
   engine/enginedevice.cpp