This commit adds a feature to load Pominal
configuration from a JSON configuration file.
A new data type called PominalConfig was created for
the purpose of configuring Pominal.
A new factory function called newPominalConfig was
created which takes the path to the JSON configuration
file and the flag overrides and generates the new
PominalConfig value.
Here, the JSON config is parsed to create the initial
configuration and any flag overrides can override
the corresponding fields in the PominalConfig object.
Currently only the sessions times and the maximum work
sessions per Pominal cycle have flag overrides.
Additionally users can now configure custom notification
messages for each session type from the configuration file.
There are currently no flag overrides for these.
This commit resolvesdananglin/Pominal#1
* replace the table driven test with sub tests.
* create and publish code coverage reports via GitLab pages.
* use JUnit to view test results in the test tab in the pipeline view.
* upgrade Go to version 1.13.6.
