Use GLib.Parameter[] to store request params

[arteymix]

The request paramters can integrate better with GObject if they consist of a list of GLib.Parameter. At first, it will be possible to unpack them in an arbitrary object and access the parameters by properties.

var obj = Object.newv (request.params);

var id = obj.property;

Then we could rework the current type system for parameters so that it can expand automatically the desired type.

var id = req.params[0].value.get_int ();

We could also use Variant serialization to store and extract data: http://valadoc.org/#!api=glib-2.0/GLib.Variant

• type would become type format
• values would be extracted seamlessly

[arteymix]

After thoughts, this PR should be reoriented as follow:

• use GLib.Parameter to store the request parameters (just the Value on the stack though)
• provide to_url to reverse a route from a sequence of parameters GLib.Parameter[]
• provide means to extract and marshall parameters (from string to Value and vice-versa) by defining functions based on GLib.Type

Also, it does not appear to be possible to store GLib.Parameter in Value, which makes it impossible to push them on the routing stack.

[arteymix]

It's possible to register type transformation functions that would convert from our types to target types: http://valadoc.org/#!api=gobject-2.0/GLib.Value.register_transform_func

Types in parameters would just become GType identifiers and extraction/marshalling would just become type transformations.

[arteymix]

Parameters will be stored in the context.