fixup lines with two closers on a line in wml test directory

wmlindent chokes on these

commit made with the following command:

find data/test/scenarios/ -type f -print0 | xargs -0 sed -i
"s|^\([[:space:]]*\[\/.*\]\)[[:space:]]*)\}[[:space:]]*$|\1\n)}|"
move unit_filter implementation out of unit

The purpose is to simplify the unit class, and perhaps allow for
some optimizations regarding how unit filters are impemented.
add filter_context class, use in unit_filter

The filter context is, game_board + tod manager.
game_display can (and now does) implement this interface,
also game_state. This permits both animations and engine
components to use it.
side_filter uses filter_context
terrain_filter uses filter_context instead of resources
replace unit filter with a function object

This allows us to separate the parsing of the filter from its
invocation, similar to the side filter and terrain filter, and
can speed things up if we move it outside of key loops
preprocess conditional children of unit filters
Merge branch 'refactor_unit_filter'