centralize getting haxelib, haxe, and nme directories to make it possible to use haxe/haxelib/nme from a maven plugin or build server in an isolated environment. use full paths to 'open' and 'xdg-open' scripts in order to support isolated environments. all of the above should be non-breaking but adds consistency to path handling to make it possible to build nme projects using a build server in a team environment.
Merge branch 'master' of https://github.com/haxenme/NME

Conflicts:
	run.n
	tools/command-line/src/CommandLineTools.hx
	tools/helpers/PathHelper.hx
	tools/run-script/RunScript.hxml
manual merge of various conflicts. hoping this doesn't goof anybody up; I have modified nme path and lib handling to make it possible to use nme from a build server, which was not possible before.