We need some refactors of CONTENTIO-170 for preparing CONTENTIO-173
Functional features missing:

• manifest.json and all *.xml files exported into the archive need to be indented for being easier for user to understand it.
• metadata for resources and resource-collections were not SAXed (last contributor, id, creation date, etc.)
• missing id for sites
• the page attachments were not exported
• always export sitemap folder (even if there is no page)
• missing order for pages

Technical features missing:

• common abstract class for Schedulable (common code for sending mail, etc. for export/import)
• ArchiveHandler component
• For interfaces Archiver, PluginArchiver, rename process into export, as it will also hold import logic
• Some helper methods (Export ACL, hashed path, ...)