Updates to AlwaysInstallElevated Local Priv Esc

Taking on @schierlm 's feedback to force the installer to fail installation so cleanup isn't required. After installation there should be nothing added in Add/Remove Programs.

 https://github.com/rapid7/metasploit-framework/pull/1090

I have added some failing VBScript to the installer so the MSI will need recompiling.

I have added an advanced option to the FileDropper exploit class to allow for a delay on cleaning up of files. This allows time for the exploit to migrate so clean-up of the payload can occur successfully.