Make substitute replace ${VARS} with environment vars if they have no value set in defines.

This allows the use of ${ANDROID_SDK} inside extensions XML files.
fix https://github.com/openfl/openfl/issues/365
Cleanup/patch legacy build XML
Build fix
Do not compile Lime debug binaries by default on rebuild
Fix iOS sim
Merge pull request #262 from shumkovdenis/master

fix https://github.com/openfl/openfl/issues/365
Merge pull request #261 from fbricker/patch-1

Make substitute replace ${VARS} with environment values.
Minor tweak
Neko GraphicsPath fix
Populate environment with HXCPP config defines
Removed double dispatch of mouse event for html5 target
Merge pull request #265 from alebianco/master

Removed double dispatch of mouse event for html5 target
Rebuild both debug and release locally when using 'lime rebuild' again, rebuild the tools when using the '-rebuild' flag
Initial improvements to 'rebuild' command and '-rebuild' flag, walking through actual project dependencies
Fix 'lime create openfl'
Merge branch 'master' of https://github.com/openfl/lime
Update openal submodule
Enable timer when window is minimized