Refactor examples

[pelesh]

Description

Several minor issues related to examples are addressed here:

• Some examples return redundant output, which may obscure important error messages.
• Distributed generator and microgrid examples did not test for result accuracy.
• Helper functions specific to Matpower parser testing were included in general GridKit testing utilities.
• Some examples built with compiler warnings.

@alexander-novo @abdourahmanbarry

Proposed changes

Comment out redundant output, add accuracy checks where missing and fix compiler warnings for all examples.

Move helper functions for Matpower parser tests to examples/PowerFlow/MatPowerTesting/MatPowerTesting.hpp.

Checklist

• All tests pass.
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows GridKit™ style guidelines.
• N/A There are unit tests for the new code.
• N/A The new code is documented.
• The feature branch is rebased with respect to the target branch.

Further comments

None.

[nkoukpaizan]

Tests currently pass. I left a few suggestions and would like to test again after they are addressed.

[nkoukpaizan]

Approving, as we've discussed that command line arguments for verbosity (#112) and the isEqual template design are out of scope for this PR.