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Settings Framework Release
* added `debug` keyword argument that takes dict and is added to base settings
only if DEBUG is true
* added importd.env, which checks a key in environment and if not present
returns a default value (so that I do not have to write this utility
everywhere)
* added a importd.debug() that can be used for conditional settings
* MIDDLEWARE_CLASSES, INSTALLED_APPS or TEMPLATE_CONTEXT_PROCESSORS is looked
for settings that starts with "debug:", such values are dropped completely in
prod, and in debug the "debug:" prefix is stripped. similarly we have "prod:".
* created impoortd.e() which can be used to "expose" some of the settings to
template. in order to use it in template, add a template context processor
"importd.esettings", this will make available a variable named "esettings".