include default github .gitignore content
Added nav specific build directories.
Merge pull request #21 from ablasdel/patch-1

include default github .gitignore content
dwa_planner: fixed bug where robot failed to turn at start of plan.
The logic in question was lost in the groovy refactor.
dwa_local_planner: removed PreferForwardCostFunction to encourage turn-in-place at start of plan execution.
PreferForwardCostFunction was introduced in groovy.
navigation 1.10.3