fixed explanations about how access control rules work
Furthering @fabpot's changes to the access_control explanations in the security chapter
tweaked text
Added missing path prefix `/admin` to access_control
Adding a small document on the changes related to trusting proxy data
Improved "Setting up Permissions"

Signed-off-by: Manuel Reinhard <manu@sprain.ch>
Update reference/dic_tags.rst
Merge pull request #2123 from gido/add_prefix_access_control

Added missing path prefix `/admin` to access_control
[#2123] Tweaking access control fix - I want to highlight how the access_control keys - unless suffixed with the regex $ - are not exact matches
Merge pull request #2131 from sprain/improving_setting_up_permissions

Improved "Setting up Permissions"
[#2131] Furthering the excellent permissions changes made by @sprain
Fixed typo, closes #2132
Merge pull request #2133 from WouterJ/patch-4

Fixed typo
Update cookbook/form/form_collections.rst
Add deprecations to PR summary
tweaked the PR check-list to make it more readable
added a shorter version of the todo list for minor changes
added more information about how to document BC breaks and deprecations
added more hints about the goals of the check-list
[#2128] Fixes per @WouterJ's suggestions