WWTMVC5/Views/Learn/SettingUp.cshtml: fix link to MIDI controller file
WWTMVC5/Views/Learn/SettingUp.cshtml: fix link to MIDI controller file

Closes #57.

It looks like there are other links in the web tree of the form
`@Model.ResLoc/Content/...` that *are* correct, so the change I'm doing here
doesn't seem to (need to) be applied globally.

WorldWideTelescope/wwt-website,WorldWideTelescope/wwt-website,WorldWideTelescope/wwt-website