Library does not work on old IE

Closes #3126

- Removed title `ModalContainerComponent`, because it is internal component

- Added title `ModalContainerComponent`

- Added section BsDropdownState
- Added section BsDropdownContainerComponent

- Added title `Trigger by tag <a>`
- Set title and anchor to be mandatory for examples

fix if state.value == null _newState.value will set to '1970-01-01 08:00:00'

* feat(datepicker): added BsLocaleService to change datepicker locale

* chore(datepicker): removed obsolete comments

* fix(datepicker): add BsLocaleService to exports

* demo(datepicker): change locale demo according to BsLocaleService

* feat(build): add es2015 support

* refactor(build): use await instead of promises

* feat(build): clear tmp folder, fix es2015 field in package.json

* chore(ci): reuse stages configuration

* chore(ci): add formatting to yaml file

* chore(ci): update utils related to release notes

* chore(ci): chrome headless is not stable

* chore(ci): firefox, please please

* chore(ci): firefox, please please

* chore(ci): use firefox for tests

* fix(datepicker): calendar repeat days (ex:. 15-oct-2017) when using safari for lang pt-br in summer time

* fix(datepicker): calendar repeat days (ex:. 15-oct-2017) when using safari for lang pt-br in summer time

fixes #3191

* chore(ci): publish to gh-pages for tagged commits

* chore(ci): publish tagged commits to npm

* chore(ci): chrome headless should work

* Add Japanese bs-moment #prepare() method

* Add Japanese bs-moment test

* Fix 'fdescribe'

fixes #2902