Update Search Form link in help/docs/introduction.aspx

[raddick]

Issue title: Link to DB query form does not work

From: Chris Karner

Category: Question

Severity: Moderate

Description:

The file '/dr13/en/tools/search/form/form.aspx' does not exist.

Steps to reproduce:

1. Go to http://skyserver.sdss.org/dr13/en/help/docs/introduction.aspx
2. Click on Link for "Search Form" in column "..then use"
   (needed: Position (RA/Dec), magnitude, and/or redshift (if DR8 includes a spectrum for that object))