Refactor out using global resources singletons in KisPaintOpSettings

Patches

Please check the commit messages of individual commits. I have split this huge patch into small logical commits.

Still to be done

1. Fix several places accessing resources from non-gui thread

• KritaPatternGenerator
• KritaFilterGradientMap
• KisFilterPalettize

2. Implement automatic loading of embedded resources to the database.

Test plan

1. Test different paintops. Pay more attention to these paintops:

• Pixel Brush
• Colorsmudge Brush
• Duplicate Brush
• Filter Brush
• Hatching Brush (!)
• TangentNormal Brush
• Bristle Brush
• Sketch Brush
• Spray Brush

2. For every brush:

• try activating Predefined Brush Tip
• try activating Texture option
• try activating Masking Brush (with predefined and non-predefined tips)
• try save/load brush