remove trailing whitespace

[mlautman]

This PR removes the trailing whitespace across the code base. It was done with this command.

find . \( -name '*.h' -o -name '*.hpp' -o -name '*.cpp' -o -name '*.c' -o -name '*.markdown' -o -name '*.md' -o -name '*.xml' -o -name '*.m' -o -name '*.txt' -o -name '*.sh' -o -name '*.launch' -o -name '*.world' -o -name '*.urdf' -o -name '*.xacro' -o -name '*.py' -o -name '*.cfg' -o -name '*.msg' -o -name '*.yml' -o -name '*.yaml' -o -name '*.rst' \) -exec sed -i 's/ *$//' '{}' ';'

[mlautman]

@aaronplusone @henningkayser