Refactor third party module and add new modules.

Refactored third party module configuration to make it simpler to add new modules. Only a module name and a description are required. This assumes that the only logic required is to check for the flag and add an --add-module flag for that module. For anything more involved, a depends_on line should be used.

This also includes a fix for an outdated shasum for the dav-ext, an incorrect share folder name for the subs-filter module, and adds a few modules.