Implement clickable source links in ui

[Kamilcuk]

Feature request: Make source links in ui interface clickable #901

[CLAassistant]

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[Kamilcuk]

<a href="http://localhost/product">/product</a>
<a href="http://localhost/product">/product</a>
<a href="http://httpsrc.com:443/">httpsrc.com:443/</a>
<a href="http://httpssrc.com:80/">httpssrc.com:80/</a>
<a href="http://www.dba.dev/auth/">www.dba.dev/auth/</a>

[KTruesdellENA]

Reviewed, discussed this and made some changes to this and made this an option to be set in the *.properties file or the cli configuration. It would default to not being enabled, but can be enabled.
Added in some options with that as well to be able to set a different protocol scheme, host, or port for these links or default to the current server address (for those links that are a subdirectory).
Also, added another option to have links open in a new tab and defaulted to a new window.

Going to branch your commit and merge things for this PR. Then you can review and see if it meets your needs.

[Kamilcuk]

Closing because https://github.com/fabiolb/fabio/pull/907 is there.