Merging LDP into main branch.

Adds basic server-side LDP support to RWW.I/O:
* Directories act as LDPCs while files are LDPRs
* Added pagination for LDPCs
* Added support for ``Accept-Post`` header

Minor fixes for ACL:
* Allow PUT for Append mode only if the resource doesn't exist.
* Clear ACL policies by doing a DELETE for .acl file if no mode is selected.

User:
* Correctly display the name and pic for the logged user.