Parametrized widgets

We already have parametrized views but a parametrized Widget would also be nice.

Current code sample:

   def _remove_recipient(self, email):
        Text(self, ".//a[text()='{}']".format(email)).click()

What I would imagine:

class Foo(View):
    w = Text(ParametrizedLocator('//something[@important={name|quote}]'))

v = "instance of Foo"
# Widget recognizes that there is a parametrized locator in args and returns a proxy
v.w == "some proxy"
v.w.read() # => triggers an error because it is a proxy
v.w(name='foobar').__locator__() == '//something[@important="foobar"]'
v.w(name='foobar').read() == "something"

Start by reading how parametrized views currently work, then trace how Text and ParametrizedLocator handle their arguments. Use the examples in the issue to define proxy behavior, locator expansion, and read behavior; done means named widget parameters produce the expected locator and usable widget operations while direct proxy reads fail as shown.