Task-Number: QTCREATORBUG-2375

While it was set to 2 for most editors, some editors, like the .pro file
editor, set another document on the BaseTextEditor, which then did not
get its cursor width set.

Also removed a duplicated line.

Reviewed-by: dt

Reviewed-by: kh1

Adapt Qt4ProjectManager to use QMLOBSERVER instead of QMLINSPECTOR
(got changed in commit a10b2692)

This also obsoletes one class and one UI file.

Reviewed-by: Alessandro Portale

Reviewed-By: dt

We should restrict ourselves to calling all qml debugging support
observer, instead of mixing qml debugger / inspector / observer
interchangeably.

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.

Unify terminology somewhat.

The class extends the QDDebugService class, _not_ QDDebugServer. It's
right that there is also a QDEngineDebugServer being actually a service
in QtDeclarative, but we should probably fix this one too.

Introduce some more private classes for the coreplugin,
use header include convention
<QtModule/QClass>, de-qobjectify VariableManager.

Task-number: QTCREATORBUG-2318

Reviewed-by: Jarek Kobus
Reviewed-by: hjk