Add the default possible win executable file extensions (including the actual used by eta cmd) so etlas exec works without extension
Although the complete list of extensions (in windows 7) is .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC, i've added only .COM;.EXE;.BAT;.CMD
Set the default executable file extension to cmd if the build os is windows so internals calls to execute programs finds the correct win script launcher (f.e. when running etlas test)
Changes:
cmd) soetlas execworks without extension.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC, i've added only.COM;.EXE;.BAT;.CMDetlas test)