For book, shelves and chapters.
Made much of the existing handling generic to entity types.
Added new MixedEntityListLoader to help load lists somewhat efficiently.
Only manually tested so far.
Adds a thin wrapper for DOMDocument to simplify and align usage within
all areas of BookStack.
Also means we move away from old depreacted mb_convert_encoding usage.
Closes#4638
Is a tweak upon the existing approach, mainly to store and query role
permission access in a way that allows muli-level states that may
override eachother. These states are represented in the new PermissionStatus
class.
This also simplifies how own permissions are stored and queried, to be
part of a single column.
Not totally happy with implementation as is requires extra service to be
injected to core controllers, but does the job.
Included test to cover.
Updated some controller properties to be typed while there.
