Add models EntryDoc, EntryHTML
Update relations Entry
Fix attribute name in entry_doc and entry_html: jahreszahl -> jahreszahlen
Add import_doc_from_html task
Add import_entry_doc_helper implementing import_entry method
Add import_entry_doc_helper_spec
Update import_html task: save lemmata as EntryHtml
Update import_html task: save lemmata as EntryHtml
Add page_reference to EntryDoc
Display html safe Entry.quellen, literatur, eigene_ergaenzungen, literatur_ergaenzungen and quellen_ergaenzungen in view
Revert "Update import_html task: save lemmata as EntryHtml"

This reverts commit 4abab69477beb17bb7d98593a3efa7a041c29df9.
Revert "Add page_reference to EntryDoc"

This reverts commit 76b4b1bc86c9ac234e878b253696a3d135c914f7.
Add import entry from doc and html task + helper and spec test