Alter configuration loading

Set the Symphony admin URL based on configuration

Set site mode based on configuration

Update installer

Migration file skeleton for 2.4

Update 2.4 migration to add new configuration value

Fix typo in installer

Typo in installer page

Fix fields names

Fix mistakes in index

Fix defines

Fix creation of Configuration

Add comment for explanation

unset erroneous symphony-page when empty
Merge branch 'admin-url' of github.com:designermonkey/symphony-2 into designermonkey-admin-url
Update migration file