feat(stark-core): allow customizing Login and Preloading states via the StarkSessionConfig

[christophercr]

ISSUES CLOSED: #727

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[X] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #727

What is the new behavior?

All "Init" and "Exit" states managed by the Stark Session module are configurable via the StarkSessionConfig object passed in the forRoot() method.

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information

Took the change to re-generate the root package-lock.json file.

[coveralls]

Coverage decreased (-0.3%) to 91.32% when pulling f8112cb on christophercr:feature/configurable-session-states into 203eaf7 on NationalBankBelgium:master.