set WebFile fpath to URL base

[jmank88]

This PR sets the fpath for WebFiles to the 'base' of the URL, which is the base of the path if non-empty, otherwise the host.
Follow up from #154

[Stebalien]

I think we need to handle files with duplicate names. That is, check to see if the file already exists in the map, and, if so, pick a new filename.

[jmank88]

Now ipfs add "http://test/test" "http://different/test" "http://another/test" "http://more/test?param=value" produces:

test
test (1)
test (2)
test (3)