create contribution event type set
emit proposal_create event for amendments
create amendment event types
emit amendment events
add amendment event icon
define amendment.selection even if selection is deleted

Without this, entity_url on a deleted amendment will fail

As amendments always have one single selection and are
below that in the hierarchy I guess it is reasonable
to keep the selection around even if it is deleted.
amendment event dashboard preview
no amendment badges
fix milestone all_proposals instance

if `adhocracy.milestone.allow_show_all_proposals` is activated,
all proposals from an instance should be displayed for each
future milestone.

Currently, all proposals from all instances are listed.
Merge pull request #618 from xi/feature-fix-milestone-all-proposals-instance

fix milestone all_proposals instance
Merge pull request #617 from xi/feature-no-amendment-badges

no amendment badges
fix edit proposal thumbnail badges in combined edit

this produced a 500 error when editing a proposal,
but only if adhocracy.proposal.split_badge_edit was false
and thumbnailbadges are available
remove defunct knockout instance badge code
create overlay-url instance badge button
pep8
refactor instance badges dialog

code copied from proposal badges dialog
Add permission page.edit_head

The page check "function == p.NORM and variant == Text.HEAD" has been
introduced in 40dd3808a9a963671a7b3582dc7bdc9f03fb12ec, disabled in
111b5522f7692df353af0ac44ce6c387a7c886b9 and reenabled in
8de31ada30bcdaa23428268b14c27a1ba0988016.

My guess why it's here in the first place is to only allow instance
admins (or higher) to edit original versions.

In current use cases however it is desired to allow changing of original
versions to other groups (i.e. moderators). Therefore this precise case
is now covered with a separate permission "page.edit_head", assigned by
default to moderators and higher.

For the general mess concerning lib.auth.page and lib.auth.norm see
#572.
Remove unneeded data dict

Fixup 0520aff3367f1f92402970427160321c8927c699
remove unneeded import
Merge pull request #620 from xi/feature-619-instance-badges

Fix instance badges