depends: fix already installed check on osx

Avoid depending on .so files which could be .dylib on osx
Fix some invalid dependencies
Better caching and updating for dynamic list provider
Cosmetic changes
Merge pull request #4271 from elupus/depends_fix

depends: fix already installed check on osx
Merge pull request #4243 from Black09/directoryprovider-extensions

Better caching and updating for dynamic list provider