Fix error message "files cannot be writing"

If the module can't write files to the system it displays this status message:

One or more files cannot be writing to the file system this is probably a permission issue. @see http://drupal.org/project/features_tools for more info

There are a few things wrong with this:

• The URL for the project page is wrong. The project name is ftools, not features_tools.
• The URL isn't hyperlinked. As a matter of user experience it should be clickable.
• It displays as a status message, but it's really an error.
• The English has grammar, punctuation, and style issues.

I propose this instead:

One or more files could not be written to the file system. This is probably a permission issue. See the Features Tools module page for more information.

Patch to follow.