Issue 7

The original for loop tried to validate the arguments passed to the
:sanitize command. Instead of checking the actual command line arguments
against the valid options, it checked the "massaged" values returned by
Sanitizer.argToPref function. The Sanitizer.argToPref function converts the
arguments 'commandline' to 'commandLine', 'offlineapps' to 'offlineApps'
and 'sitesettings' to 'siteSettings' for things to work properly further
down the chain.

The original validation failed when the user asked for ":sanitize
commandline" because the converted 'commandLine' was not a valid sanitize
option. The same happened for ":sanitize offlineapps" and ":sanitize
sitesettings".

The new for loop validates the actual command line arguments passed to
:sanitize against the valid sanitize options.