Fix :n debug command
Merge pull request #236 from aquileia/next_level

Fix :n debug command
run a headless mp test game as part of the travis clang builds
give an error message when we crash from bad command line args

This only fixes one case but when you are trying to set up a
headless multiplayer game it is pretty annoying when it crashes
with no explanation because of a bad controller string.
filters hold safe vconfig, const vconfigs can call make safe
give better error messages when we can't parse command line args
also run ai test with gui on
cleanup travis yml file (don't need [[, ]])
travis.yml: put time outside of multiline if
add line breaks between the sections in .travis.yml
fixup minor travis after_failure logic
remove the play_test with gui from travis script, it doesn't work
store child unit filters in a vector not a ptr_vector

this is possible now because unit filters were made copyable
in an earlier commit, I think when they were added to animations
fix syntax error in .travis.yml
move is_observer from game_board to display_context, b/c editor uses
move a barely used function out of unit into statistics
remove pointless static singleton getter for teams
fixup map label segfault in editor
Merge branch 'fixup_editor'
remove pointless "team::nteams()" static getter