Issue: File bbcode improvements for non-existing attachments (e.g. red links)

Hi pegasus,

Firstly I'd just like to offer my compliments to 4.1 so far. It is encouraging to witness the journey towards VW 4.1.x through the progress sidebar and various feature requests being marked as implemented.

As for the feature request, this can be broken down into two parts.

1) Red links: Unlike regular wiki links, [file] bbcode links that reference an incorrect page (missing, doesn't exist yet etc) are not styled in red. Implementing [file] red links would make it much clearer to see when there is a link issue.

I have provided a little experiment in the wiki area of this site showing the red link differences between standard and file bbcode wiki links: https://www.vaultwiki.org/demo/Sort-...-not-exist-TBA

2) itemtypeid: When a [file] link is clicked and the destination page does not exist, the create tab does not currently display an upload file field. Manually changing "itemtypeid=1" to "itemtypeid=9" on VaultWiki.org displays the desired behaviour. It would be fantastic if VaultWiki could track how someone arrives at a red link (regular link? file bbcode link?) and, if appropriate, include the file upload field.

Combined with part 1, this would also offer another method for uploading files:

1. -Manually type in a file name wrapped in file tag
2. -Save changes to the wiki page
3. -Click the file red link
4. -Click "create"
5. -Proceed to upload the file, add details and submit
6. -Reload the previous wiki page and see that the image is embedded (as a thumbnail, etc).

Thanks