fix query_param encoding
tweak text
pin versions
typo
rm missing static links

We can not guarrantee that these pages will be available in
every static pages backend.
update sass and compass to latest versions
use compass flexbox mixins
clean up openid template
sso warning
update ssh warning text and add button
update sseo warning CSS
static page on instance overview
clearify instance static_overview_path comment
Merge pull request #814 from xi/feature-static-instance-overview

static page on instance overview
Merge pull request #813 from xi/feature-984-velruse-ui+3

single sign-on warning
i18n
Use proper permission check for edit category button

Fixup 545c9ec084a47ed5dd3a96799728e0db3aac9eec from PR #805
Fix avatar display for users with underscore (fixes #811)

Contrary to the validation notice, it is possible to create user with an
underscore in the username. However when doing so, the avatar wasn't
shown due to a route matching issue.

In order to avoid that, this commit changes the avater URL to use the
user id instead of the username. This results in less nice avatar image
urls, but this doesn't really matter much.
Merge pull request #808 from xi/feature-query-encoding

fix query_param encoding
make event controller work on instances