Enable setting breakpoints, and showing the script console even if
the QmlInspector plugin is not loaded.

Reviewed-by: hjk

namespace (from Debugger::Internal) as they are exported classes.
Introduce private classes to avoid exposing private JS debugger
headers.

Reviewed by: Lasse Holmstedt

Reviewed-by: hjk

A new debugger engine, QmlCppEngine, is introduced, which wraps gdb
and qml engines into one. Alternatively, if using Windows, Cdb is used
instead of Gdb.

Most of the debugger ui switcher is now rewritten, and it is tailored
for the QML and CPP layout case, the only one supported anyway.

Reviewed-by: hjk

Now, QmlEngine creates the connection to the inferior (debuggee), and
notifies QmlInspector when a connection is established. Before,
inspector created the debugger engin, which was wrong.

QmlEngine's responsibilities are connecting to the debuggee and basic
QML/JS debugging features like locals & watchers, breakpoints etc.
QmlInspector takes care of Live Preview and other fancy inspection
features.

Reviewed-by: hjk

For starters, we only remember whether the initial warning about dangers
of Live Preview was shown.

The crumble path shows the current context of the debugger/inspector.

Two kinds of warnings are now shown: one for warning about the Live
Preview itself, as it is experimental, and another when user changes
id's of objects during runtime, as this is not supported at the moment.

More warnings will be added later for other unsupported changes.

The button is checkable and pressing it will stop/propagate changes to
the qml application being debugged.

A mostly mechanical change.

Reviewed-By: con

Discussed-with: hjk

Task-number: QTCREATORBUG-1288

It's not yet possible to attach to an external app running a qml
debugging server, because the server is only started on startup if an
env variable is set. Changing this requires action from Brisbane, but
even the current solution works for C++ apps with QML in them.

Task-number: BAUHAUS-585
Reviewed-by: dt

Reviewed-by: hjk

the previous implementation relied on poking around with setVisible
of the menu actions. Now, command attribute CA_Hide is used instead for
the necessary entries.

Reviewed-by: hjk