Modified ParaView macros to use both Qt4 and Qt5

Depending on the PARAVIEW_QT_VERSION variable value, the appropriate Qt version
is used.
Change-Id: I595069f00809082e30770e0c3e2dcd14ef8f69ae
Import Qt5Widgets module at the top level

This ensures all the required Qt5 variables can be found.
For example, just importing Qt5Core does not help find QT_UIC_EXECUTABLE using
the macro "get_target_property(QT_UIC_EXECUTABLE Qt5::uic LOCATION)". This must
be a Qt5 bug.

Change-Id: Ie6f4a708682ad8cf2391d218c193d8127e4c44f7