Update utilities and examples pages

Author: ikorotkin

docs/examples.md

@@ -11,7 +11,24 @@ Work in progress
 
 ## Quick Start
 
+The Quick Start example can be found in the [Quick Start](quick-start.html) section and in the [quick_start.cpp](https://github.com/dae-cpp/dae-cpp/blob/master/examples/quick_start/quick_start.cpp) source file.
+{: .fs-5 .fw-400 }
+
+A basic example of how to start solving a very simple DAE using the [`System`](solve.html#system-class) class.
+
 ## Simple DAE
 
+Simple DAE source file example: [simple_dae.cpp](https://github.com/dae-cpp/dae-cpp/blob/master/examples/simple_dae/simple_dae.cpp)
+{: .fs-5 .fw-400 }
+
+Here we solve another simple system of DAEs.
+This example introduces [Solution Manager](solution-manager.html), that will work as solution observer.
+
 ## Perovskite model
 
+Perovskite model source file example: [perovskite.cpp](https://github.com/dae-cpp/dae-cpp/blob/master/examples/perovskite_model/perovskite.cpp)
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+
+A more sophisticated example, where we solve a big DAE system that describes potential distribution and ion concentration in a perovskite solar cell.
+We show how to add parameters to the user-defined mass matrix, vector function, and Jacobian.
+This example also demonstrates a custom [Solution Manager](solution-manager.html) implementation that can work as an observer and event function.

docs/utilities.md

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 nav_order: 9
 ---
 
-Work in progress
-{: .label .label-red }
-
 # Utility functions and constants
 
-TODO:
+This section describes utility functions and constants that can be useful in the user's project.
+
+## Get the solver version
+
+The current version of `dae-cpp` can be obtained either by using the following macro:
+
+```cpp
+DAECPP_VERSION_MAJOR
+DAECPP_VERSION_MINOR
+DAECPP_VERSION_PATCH
+```
+
+or by accessing the following constants (`static constexpr uint16_t`) in the `daecpp` namespace:
+
+```cpp
+daecpp::version_major
+daecpp::version_minor
+daecpp::version_patch
+```
+
+## Timer
+
+`dae-cpp` provides a simple timer based on `std::chrono::steady_clock` which is used internally in the solver, but it is also exposed for the user in the `daecpp` namespace.
+The timer measures time spent by the program in the given scope and saves it in **milliseconds** in a variable of type `double`:
+
+```cpp
+double time{0.0}; // Stores time (in ms)
+{
+    daecpp::Timer timer(&time); // Starts the timer
+
+    // << TASK >>
+
+} // End of scope stops the timer
+```
+
+In the example above, we initialize the variable `time`, which will store the time in milliseconds.
+Then we define the scope and create an object of class `daecpp::Timer` by passing the address of the variable `time`. Constructing this object starts the timer. When we reach the end of the scope that we defined, the `timer` object will be destroyed. This stops the timer, and the computation time (in milliseconds) will be written into the `time` variable.
 
-- [ ] Get solver version
-- [ ] Timer
+Note that the `time` variable can be reused. We can start a new timer in another scope passing the address of `time` again. The computation time will be added to the previous value.