COMP 12945: Allow VTK to build against Qt5

Since VTK build system has been updated to make use of CMake macros
specific to Qt5, the support has to explicitly enabled configuring VTK
with -DVTK_QT_VERSION:STRING="5"

Additionally, in case Qt5 is not installed in a standard location,
a custom prefix for "find_package" should be passed.
For example:
  -DCMAKE_PREFIX_PATH:STRING=/home/jchris/Qt5.0.2/5.0.2/gcc_64/


Finally, this commit also resolves the build errors reported below.

Fix missing header build error by including Qt headers directly without
specifying the intermediate directory.

* Fix build error changing QString::toAscii into  QString::toLatin
The method "toAscii" has been deprecated and is not available in
default Qt5 distribution.
See http://qt-project.org/doc/qt-5.0/qtcore/qstring.html#toAscii

* Fix build error changing Qt::WFlags into Qt::WindowFlags
See http://qt-project.org/doc/qt-5.0/qtcore/qt-obsolete.html

* Fix build error changing QAbstractItemModel::reset() into
combo QAbstractItemModel::beginResetModel()/QAbstractItemModel::endResetModel()
The method "reset" has been deprecated and is not available in
default Qt5 distribution.
See http://qt-project.org/doc/qt-5.0/qtcore/qabstractitemmodel-compat.html#reset

* Fix build error by including "vtkObjectBase.h":
/home/jchris/Projects/Qt5.0.2/5.0.2/gcc_64/include/QtCore/qmetatype.h:464: error: invalid application of ‘sizeof’ to incomplete type ‘QStaticAssertFailure<false>’

* Fix "no matching function for call to ‘QPixmap::grabWidget(QWidget*)’" by using
"QWidget::grab"
See http://qt-project.org/doc/qt-5.0/qtwidgets/qwidget.html#grab

* Fix missing QHttpHeader/QHttpRequestHeader headers by removing them.
They have been removed from Qt5 and were not used in the code.

* Fix error: ‘qInstallMsgHandler’ was not declared in this scope
by using "qInstallMessageHandler"
See http://qt-project.org/doc/qt-5.0/qtdoc/sourcebreaks.html

* Fix Q4VTKWidgetPlugin.cxx:147: error: invalid application of
‘sizeof’ to incomplete type ‘QStaticAssertFailure<false>’ by
using "Q_PLUGIN_METADATA" macro instead of Q_EXPORT_PLUGIN
or Q_EXPORT_PLUGIN2.
See http://qt-project.org/wiki/Transition_from_Qt_4.x_to_Qt5#7ec1b8f08d7f31ebcb53188f0bd15ed5

Change-Id: Ie7123e5990e3a8afb4d7d2efa0fda5bd7b98c1e3
Merge topic '12945-qt5-compat' into master

384636ec COMP 12945: Allow VTK to build against Qt5