Update scheduled tasks if definition changed

With this patch, when we update the command or the user, and if we set
"force" to true, then the scheduled task is updated.

BTW, I see in https://github.com/opscode-cookbooks/windows/blob/master/CONTRIBUTING that I should open a Jira task to contribute. However, according to http://www.getchef.com/blog/2014/06/16/chef-issue-tracking-and-contribution-workflow-updates/ I believe that this file is outdated. Please feel free to tell me If I'm wrong.
As @brugidou I'm not sure this is the best thing to do.
With this solution `command\with\backslashes\between\words` will be detected has equal to `com\mand\withback\slashes\bet\ween\wor\ds`

You should update the `:create` action to escape all `"` in the command only when the `schtask /Create` is run.
With this fix, the string returned by the `schtask /Query` command will be equals to the original `@current_resource.command`.
However, this is a breaking change for all other guy who used to escape double quotes manually.