Added http-host frontend param

This change add a 'http-host' parameter in the /data/params list of values.

The 'http-host' value is set to be the value of the HTTP_HOST constant.
Merge pull request #2136 from DeuxHuitHuit/current-domain

Added `http-host` page parameter
Fix typo in bundle.php
Merge pull request #2206 from DavidOliver/bundle-typo

Fix typo in bundle.php
Add missing quotes for Cache delete calls. Fixes #2202
Simplify the navigation item access for AdminstrationPage
Simplify parent/child navigation item creation
Release 2.5.1