fix(datepicker):selectcorrectmonthandyearfrommonthpickerview…

… when displayMonths > 1 Fixes #4500 PR Checklist Before creating new PR, please take a look at checklist below to make sure that you’ve done everything that needs to be done before we can merge it. [x] read and followed the CONTRIBUTING.md guide. [x] built and tested the changes locally. [x] added/updated tests. [ ] added/updated API documentation. [ ] added/updated demos. This question comes from an open source project: valor-software/ngx-bootstrap Tested in Chrome, FF – latest, looks good. Need to update test for not disabling ts-lint rules and ready for merge.