http://www.80sprogrammer.com/2012/08/16/%E8%AE%A9myinvocation%E5%91%8A%E8%AF%89%E4%BD%A0%E8%84%9A%E6%9C%AC%E8%BF%90%E8%A1%8C%E7%9A%84%E7%9B%AE%E5%BD%95/
http://blogs.msdn.com/b/powershell/archive/2006/07/06/how-can-a-script-tell-what-directory-it-was-run-from.aspx
http://connect.microsoft.com/PowerShell/feedback/details/746643/myinvocation-mycommand-path-is-null-when-importing-a-script-file-from-a-module-file-psm1
$Myinvocation
http://technet.microsoft.com/en-us/library/hh847768.aspx
