Fix the removal of start menu shortcuts for windows agent

Refer to
http://nsis.sourceforge.net/Shortcuts_removal_fails_on_Windows_Vista.
This fixes issues on machines that run Vista or newer.
Allow NIX agent to use "-f" option and run in foreground
Merge pull request #11 from bb2gh-ossec/awiddersheim_fix_windows_start_uninstall

Fix the removal of start menu shortcuts for windows agent
Merge pull request #16 from bb2gh-ossec/awiddersheim_fix_nix_agent_foreground

Allow NIX agent to use "-f" option and run in foreground
Merge remote-tracking branch 'upstream/master'