Attempting to rename clocked. (modelica#3313)

* Attempting to rename clocked.
* Since discretized is part of clocked.
* Better formatting to make it readable.
* Try to be clear with sub-clock/base-clock.
* Be clear with partitions, found when adding sub-clock/base-clock.
* Introducing discretized.
* Major change with new separatio of different kinds of paritions.
* Cleaned up.
* Clean up index.
* Use sub-partition and base-partition.
* Add conversion operators (the term, not the individual ones) to index.
* Line break and explain clock vs clocked partition.
Closes modelica#3091

Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>
Co-authored-by: Elena Shmoylova <eshmoylova@users.noreply.github.com>

chapters/statemachines.tex

@@ -30,10 +30,9 @@ \chapter{State Machines}\label{state-machines}
   in Statecharts or in Lucid Synchrone state machines but only
   indirectly with appropriate conditions on transitions.
 \item
-  Modelica blocks can be used as states. They might contain
-  clocked or clocked discretized continuous-time equations (in the
-  latter case, the equations are integrated between the previous and the
-  next clock tick, if the corresponding state is active).
+  Modelica blocks can be used as states.
+  They might contain clocked equations.
+  If the equations are discretized, they are integrated between the previous and the next clock tick, if the corresponding state is active.
 \end{itemize}
 
 \section{Transitions}\label{transitions}
@@ -342,7 +341,7 @@ \subsection{Reset Handling}\label{reset-handling}
 
 \subsection{Activation Handling}\label{activation-handling}
 
-When a state is suspended its equations should not be executed, and its variables keep their values -- including state-variables in clocked discretized continuous-time equations.
+When a state is suspended, its equations should not be executed, and its variables keep their values -- including state-variables in discretized equations.
 
 The execution of a sub-state machine has to be suspended when its
 enclosing state is not active. This activation flag is given as a