Support more file types for "Detailed Help" link

[David_L]

The detailed help link in the LabVIEW Context Help window is a great way to add extra documentation to your LabVIEW code.  However it currently only supports .hlp, .chm, .htm, and .html files types.  This should support many more documentation types such as pdf, txt, doc, .xls, png, .etc, etc.

[RDR]

It would also be nice to have native support for these other filetypes in the Help menu so the _browser.llb VIs are no longer necessary.

[SteenSchmidt]

I usually embed other file types in an HTML wrapper document, but it would be much nicer to be able to skip this step. Kudos!