Allow servers that return html with absolute links

[bikemike]

Convert absolute links to relative links

[fangfufu]

This PR could help solving,
#107

Have you thought about the approach taken here - extract the full link? I am thinking of simply allowing absolute link, rather than converting to relative link.
2ef9154?diff=split#r103774983

[bikemike]

At first I thought the best way would be to check the absolute links against the parent directory path. If the links contained the parent directory path, then remove that portion. If the resulting relative link did not contain any more slashes then it is valid, otherwise it points to a different folder location and should be ignored.

But I didn't see a quick method to get the parent directory path in HTML_to_LinkTable so I just made the links relative assuming that the server wasn't returning links to other directory locations.

Using the basename function might be a simpler solution that what I've done but at the time I initially wrote this code I think I thought that directories needed the "/" on the end. The basename function removes that last "/".

If you want to allow absolute links then linkname_to_LinkType will need a small change as it only allows relative links.

[fangfufu]

@bikemike , I decided to merge in #121, so I am closing this. Thanks for trying to help though!