Diff for Doc/Dev/Registry between 8 and 9

+ The Registry (Horde_Registry)

**##red|This information is valid for Horde 4 and later only. See ((Doc/Dev/RegistryH3)) for Horde 3.##**

Horde's Registry is the sole method to initialize the Horde environment and is the glue that holds different applications together.

* The Registry is responsible for handling authentication to the Horde framework.
* The Registry system keeps track of Horde's application stack, and which app is currently running.
* When you switch applications, the registry will take care of correctly switching the gettext textdomain, loading the application configuration, and loading the user's application preferences.
* It also lets you determine configuration information about installed applications.
* The Registry lets you generate links to other apps.
 * Links will be to the application that provides the functionality.
 * Any arguments that the target script needs (headers for an email, for instance) will be filled out of the second argument to link().
* The Registry also lets you invoke methods in other applications
 * The registry.php config file defines where to find the code necessary to execute the method, and what application implements it.
 * Any application can be integrated this way; all you need to do is map it to the registry interface.

Things the Registry does when being instantiated:

# Importing the global configuration
# Setting up configuration of various framework libraries (via Horde_Injector)
# Setting up the session handler and starting the session (including necessary authentication)
# Setting the language and gettext domain
# Restoring the registry information from cache or loading and parsing the registry configuration from {{config/registry.php}}
# Instantiating the global ((Doc/Dev/PermsPackage|Permission)) object (TODO: should be removed in favor of Horde_Injector)

((Doc/Dev/RegistryUsage|Click here)) for Registry usage examples.

[https://github.com/horde/base/blob/master/horde/config/registry.php[https://github.com/horde/base/blob/master/config/registry.php Click here] for documentation on how to configure the {{horde/config/registry.php}} file.