Improve the code and API in a few ways:
- Expose a more discoverable "request" argument in the signal.
- Use the request as the carrier of the backend WebContentsAdapter
  and get rid of our handle.
- Put the adoption method (renamed to openIn) on the request object
  and keep the view API clean of a context-specific adoptHandle method.
- Use an enum instead of strings for the new view destination.
- Do not let JavaScript own the request object since it won't be
  necessary until we want to support asynchronous view attachment.
  We can create the request object on the heap and let the JavaScript
  engine own the object once we want to support it.
- Move the request class to its own header.
- Replace tabs.currentView by currentWebView in the quicknanobrowser
  qml code since we now need this property on the root object anyway.

Change-Id: I40d7d15255f516ead9f3e414dd587bf345e6ca4b
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

This only move files without adjusting any paths.

This moves:
- lib/quick -> src/webengine/api (API files)
  lib/quick -> src/webengine (other files)
  This contains the main QtWebEngine module library since
  <ec7b2ee7

>.
- lib/widgets -> src/webenginewidgets
  Also rename this directory to match its module name and rename Api to api.
- lib -> src/core
- process -> src/process
- resources -> src/core/resources
- tools/* -> tools/scripts/

The build directory is spread as follow:
- build/build.pro -> src/core/gyp_run.pro
- build/qmake_extras/* -> src/core/ (for the host and target .pro files)
- build/qmake -> tools/qmake
- Build related scripts -> tools/buildscripts

Change-Id: I0cded1de772c99c0c1da6536c9afea353236b4a1
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Reviewed-by: Andras Becsi <andras.becsi@digia.com>

Introduce a few more bits of our own very basic implementations
(URLRequestContextGetter and NetworkDelegate subclasses).

Still need to figure out the appropriate dependancies in blinq.gypi

We now have our own minimalistic subclass, which still makes use of
some shell parts.