Fixed XSS in snippets generator

Under certain circumstances, parts of the client-supplied URL path would
be used in the "canonical" <link>, and no HTML-encoding was applied to
secure this, causing a reflected XSS vulnerability.

I have not been able to reproduce the exploit on my test environment,
but I have verified it on another system.
A parser for more complex permission queries
Extended permission query syntax

Now supports combining permission checks with "and" and "or".
Front-end permission checks
Changed hard failure to warning for missing permission rules

(the dreaded "the permission X is not assigned to any roles" error)
Added inline documentation on permissions
Revert "Added inline documentation on permissions"

This reverts commit a4e5fab1cb5ae5f1b4adbceee1c8de29b5967253.
Revert "Changed hard failure to warning for missing permission rules"

This reverts commit 2226f2decf38b4ffc4cf34130f2d3822081cec29.
Revert "Front-end permission checks"

This reverts commit 4b668b35c7c1246391fc045076b7ecc1eb3c3c77.
Revert "Extended permission query syntax"

This reverts commit 445a0857933b359fa204c378d1d3182720e8afc5.
Added confirmation for unlocking the slug. Might help with people inadvertently breaking links. Fixes #1364
MenuEditor extension 1.7.0: minor bugfix and italian translation

Courtesy of @iplume
Merge pull request #1369 from bacbos/master

MenuEditor extension 1.7.0: minor bugfix and italian translation
Show stack on edit pages, even if it's empty. Fixes #1307
Fixing path to new uploader for Stack.
Revert "Revert "Extended permission query syntax""

This reverts commit 595a8af6c2e32d31f4b9df0dd504a8db0a9f9826.
Revert "Revert "Front-end permission checks""

This reverts commit 1512a6cae6eab4291586cf8037039dfab080305c.
Revert "Revert "Changed hard failure to warning for missing permission rules""

This reverts commit 687196d850bd03dfeba77014b295d51e228e1cc3.
Revert "Revert "Added inline documentation on permissions""

This reverts commit 6dfb9939c39060300fa4e0562d6f88fbfe6bbe85.
Fixed permission parser bugs