backup: implement all the rest of activities backup

We should implement all these:

assignment: already done with subplugin support.
chat: already done
choice: already done
data: already done not using subplugin support. Also see MDL-22558
feedback: already done
folder: already done
forum: already done
glossary: already done
hotpot: requires work on module - halted
imscp: already done
label
lesson: already done
page: already done
quiz: already done
resource (file): already done
scorm: already done
survey: already done
url (andrew): already done
wiki (ludo):already done
workshop (david): done including subplugin support

Legend:

implemented
reserved / in progress
todo
cannot be done yet - requires backup stuff
cannot be done yet - requires bug fixing