Link now caches imports. That means importing the same library (say, Qt)
from more than one file no longer creates an importing namespace for
each one. Instead, a single one is created for the instance of Link.

To make this work, the type environment in ScopeChain has been given its
own type: Interpreter::TypeEnvironment. That has the added benefit of
being able to carry meta-information about imports. You can use
TypeEnvironment::importInfo(qmlComponentName) to get information about
the import node that caused the import of the component.

In preparation for caching Contexts.

Reviewed-by: Erik Verbruggen

Task-number: QTCREATORBUG-1736

Task-number: QTCREATORBUG-1757

The function was not used and made no sense.

Task-number: QTCREATORBUG-1388
Reviewed-by: Roberto Raggi

This used to contain all functions declared in Script blocks. With them
gone, there's no reason to keep it.

Also, a class name is added in qmjs::bind so that we have a class name
for custom properties defined inside a component.

They had not yet been updated to the new way of importing javascript.

Reviewed-by: Erik Verbruggen

Allows completion of local variable and function names.

Task-number: QTCREATORBUG-942
Reviewed-by: Roberto Raggi

Previously we just scanned every directory containing a qml file for
other qml files.

This makes import ".." work.

Reviewed-by: Erik Verbruggen

* Fill the snapshot with files that could be imported.
* Implement package imports.

* The qmldir file is not parsed yet.

Reviewed-by: Erik Verbruggen

* The "Script" type is now implicitly available without imports.
* No errors for bindings inside a Connections element.

Reviewed-by: Roberto Raggi

* For JS files: Add each Qml component that sources the file in a Script
  tag to the scope chain.
* For Qml components: Add each component that instantiates the component
  to the scope chain.
* Generate the full list of documents required for completion in a
  given file. Previously, files that included the file were missing.

There is no reason to store the Bind object in a QSharedPointer because the `binder' has the same
lifetime of its document.

Done-with: ckamm

* Support for lookup JS vs Qml
* Bind global variables.

Done-with: ckamm

Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>