Added template engine to samples

Added a grunt task to take partial HTML files and merge them with a
template file to create the full sample files. This allows us to
maintain the layout of the samples in one place. During development run
'grunt watch' to have samples automatically rebuilt.
Updated link address
Updated README

Added note that the directives do not work with the Ignite UI ASP.NET MVC Helpers
Grid markup: Unit Price column and editors are now numeric; Master-Detail: restore original state on cancel/error