Reworked ManifestsManager.clean() to use ManifestsManager.manifestSections()
Reworked ManifestsManager.clean() to use ManifestsManager.manifestSections()

This makes ManifestsManager.clean() iterate over all sections, and then
for each section get all the manifest files. Just gives us some code
reuse and improves encapsulation for ManifestSection.

webmaster128/clcache,webmaster128/clcache,webmaster128/clcache