Drop SOURCE1 and holes support.
Added SOURCEx_URL_FULL support.

Create SOURCEx_URL_FULL from SOURCEx_URL/SOURCEx if SOURCEx_URL is provided.
Use SOURCEx_URL_FULL everywhere else. Download plugins will now get the
full url including the filename.
Added compatibility with SOURCEx_URL for download plugins.
Merge pull request #85 from cavalier38/SOURCE_URL_FULL

Source url full