Add a page for creation of new System Settings in Debug Mode

In-Portal has very powerful configuration system (over 300 configuration variables), but no way to add new ones or change definition (not value) of existing ones.

To solve this I propose to:

1. add "Add" button in each configuration section
2. when pressed "Add" button would open new configuration variable adding form, where user can easily add new setting to current configuration section; this we can also validate developer input to prevent mistakes
3. add small "Edit" link next to configuration variable name to be able to change configuration variable definition at any time.