Adding "osmc_symbol_black" to category "osmc" in rendering_types.xml

In Poland, marking hiking trails are available in five standard colors: red, green, yellow, blue and black.

OsmAnd in the current version 1.5.2 renders only four colors: red, green, yellow and blue. There is no rendering trails in black.

I would like to ask for the rendering for the following combination of tags: osmc: symbol: black: white: black_bar
Merge pull request #59 from KKlim/patch-1

Adding "osmc_symbol_black" to category "osmc" in rendering_types.xml