Doc: Update the "Running Applications" topic
Doc: Update the "Running Applications" topic

Remove reference to Qt 4.8 and setting the PATH.
Add a general statement about running apps.
Use Qt Creator as the example project, because it contains
several products.

Change-Id: I31756e5d33a6783ae94bc2edf9dff3b5c5dc8ad3
Reviewed-by: Jake Petroules <2d627e1cecd5435752fa500bacbe05f7cc90c369@qt.io>

qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs