Add support for "new-style grids" and "model master views".

Finally, an API that makes some sense...  We don't yet have feature parity
with the old-style grids and CRUD views, but this is already a significant
improvement to the design.  Still needs a lot of docs though...

docs/api/views/master.rst

@@ -0,0 +1,78 @@
+.. -*- coding: utf-8 -*-
+
+``tailbone.views.master``
+=========================
+
+.. module:: tailbone.views.master
+
+Model Master View
+------------------
+
+This module contains the "model master" view class.  This is a convenience
+abstraction which provides some patterns/consistency for the typical set of
+views needed to expose a table's data for viewing/editing/etc.  Usually this
+means providing something like the following view methods for a model:
+
+* index (list/filter)
+* create
+* view
+* edit
+* delete
+
+The actual list of provided view methods will depend on usage.  Generally
+speaking, each view method which is provided by the master class may be
+configured in some way by the subclass (e.g. add extra filters to a grid).
+
+.. autoclass:: MasterView
+
+   .. automethod:: index
+
+   .. automethod:: create
+
+   .. automethod:: view
+
+   .. automethod:: edit
+
+   .. automethod:: delete
+
+Attributes to Override
+----------------------
+
+The following is a list of attributes which you can (and in some cases must)
+override when defining your subclass.
+
+   .. attribute:: MasterView.model_class
+
+      All master view subclasses *must* define this attribute.  Its value must
+      be a data model class which has been mapped via SQLAlchemy, e.g.
+      ``rattail.db.model.Product``.
+
+   .. attribute:: MasterView.normalized_model_name
+
+      Name of the model class which has been "normalized" for the sake of usage
+      as a key (for grid settings etc.).  If not defined by the subclass, the
+      default will be the lower-cased model class name, e.g. 'product'.
+
+   .. attribute:: grid_key
+
+      Unique value to be used as a key for the grid settings, etc.  If not
+      defined by the subclass, the normalized model name will be used.
+
+   .. attribute:: MasterView.route_prefix
+
+      Value with which all routes provided by the view class will be prefixed.
+      If not defined by the subclass, a default will be constructed by simply
+      adding an 's' to the end of the normalized model name, e.g. 'products'.
+      
+   .. attribute:: MasterView.grid_factory
+
+      Factory callable to be used when creating new grid instances; defaults to
+      :class:`tailbone.newgrids.alchemy.AlchemyGrid`.
+
+.. Methods to Override
+.. -------------------
+.. 
+.. The following is a list of methods which you can override when defining your
+.. subclass.
+.. 
+..    .. automethod:: MasterView.get_settings