Updated documentation with new sections on Physics and FAQ

doc/RTD/FAQ/index.rst

+.. _GettingStarted:
+
+Frequently Asked Questions
+==========================
+
+1)
+
+2)
+
+3)
+
+4)
+
+5)
+
+.. toctree::
+   :maxdepth: 1

doc/RTD/Motivation/index.rst

 .. _GettingStarted:
 
 What is the Motivation for SWIFT?
-=========================
+=================================
 
 SWIFT is designing with parallelism from the very start. It is a bottom up approach with a task based 
 parallel infrastructure at it's very core. 
+
 .. toctree::
    :maxdepth: 1
-
-   building_enzo.rst
-   RunTestProblem.rst
-   RunCosmologySimulation.rst
-   SampleParameterFiles.rst
-   WritingParameterFiles.rst
-   DataAnalysisBasics.rst
-   ControllingDataOutput.rst

doc/RTD/Physics/SPH/index.rst

+.. _GettingStarted:
+
+Smooth Particle Hydrodynamics
+=============================
+
+SWIFT simulates the universe using SPH. 
+ 
+.. toctree::
+   :maxdepth: 1

doc/RTD/Physics/index.rst

+.. _GettingStarted:
+
+What Physics does SWIFT Simulate?
+=================================
+
+
+.. toctree::
+   :maxdepth: 1
+
+   SPH/index.rst

doc/RTD/index.rst

@@ -17,7 +17,7 @@ Contents:
    Motivation/index.rst
    TaskBasedParallelism/index.rst
    FAQ/index.rst
-   
+   Physics/index.rst
 
 
 Indices and tables