1. Added cascade filter.
This is the main feature introduced in this version. The cascade filter is a new kind of keywords filter.
In the "standard" filter the photos can be filtered by a set of keywords - for example filter all photos that contain keywords "word1" and "word2".
If there are many keywords defined it is not always clear in what combinations keywords are stored in photos.
For example many photos can contain keywords "word1" and "word2", but no photo contains both "word1" and "word2".
In this case a standard filter will produce an empty set of photos.
With the new cascade filter only existing keyword combinations can be used.
When a keyword is selected in the first keywords list the second keywords list is populated only with keywords that can be found in combinations with the first keyword.
Clicking on the keyword in the second list the third keywords list is populated only with the keywords that can be found in combinations with both first and second keywords.
The third, fourth and so on keyword list can be clicked and only existing keyword combinations can be selected.
2. Changed font in filters.
The font (size, color, etc.) is changed in the "Filter" and in the new "Cascade filter".
Now the font is the same as the font in the main keywords list. Also the open size of filter windows is enlarged.
3. Several small improvements in the UI.