Add a debug option into the config.py. We will use it later.
Add the context module to contain the template lookup instance.

Now the TemplateLookup instance is created in the context module, and
all module should get TemplateLookup instance from the context.

In the futhure, we will also add the database instance into the context
module.
Add the options support, and seperate options process from context.

Now every module shouldn't use options in the global scope (becaus
have been not parse yet). And they shouldn't use the context object
in the global scope because the context should prepare after the
config parsing.

There may be some wrong (it's complex now). I think I should
restructure it in the futhure.