Changelog:

• Fixed background_color parameter being completely ignored in raster renders. Thanks to @totalretribution reporting the issue.
• Changed default color map used by Project render_raster()to DEFAULT_ALPHA_COLOR_MAP as DEFAULT_COLOR_MAP resulted in images with layers obfuscating each other in counter intuitive way.
• Unified gray shades of non-alpha and alpha variant of SOLDER_MASK preset color scheme.