Add support for linking to an IndyScan instance.

[WadeBarnes]

The link to INDY_SCAN_URL is opened in a separate tab.

Example cmd line:

./manage start "INDY_SCAN_URL=http://localhost:3707/home/BCOVRIN_TEST" "INDY_SCAN_TEXT=BCovrin Scan"

UI Examples:

With INDY_SCAN_URL and INDY_SCAN_TEXT set:

With just INDY_SCAN_URL set:

With neither INDY_SCAN_URL or INDY_SCAN_TEXT set:

[swcurran]

Approved — but I’ll leave it to you to perhaps add a bit to the documentation per my comment.