BAP-5985: Add SystemCalendar entity
BAP-5987: Add providers for system calendar
- added system and public system calendars
- updated calendar event repository
- added systemcalendar repository
- added provide4rs as services
BAP-5988: Add system calendars to System navigation menu
BAP-5987: Add providers for system calendar
- added providers unit tests
Merge branch 'feature/BAP-5251' into ticket/BAP-5985
BAP-5985: Add SystemCalendar entity;
- reduced name length of calendarEvent indexes
- modified setters for nullable attributes of calendarEvent entity
- added LogicException to calendarEvent::getReminderData
- name and is_public now are required attributes of systemCalendar entity
- added comments
BAP-5985: Add SystemCalendar entity;
- modified comment
BAP-5985: Add SystemCalendar entity
Merge pull request #3163 from laboro/ticket/BAP-5985

BAP-5985: Add SystemCalendar entity
Merge branch 'feature/BAP-5251' of github.com:laboro/platform into ticket/BAP-5987
BAP-5251: System and User Calendars. Prepare to back-merge with master
Merge branch 'master' into feature/BAP-5251

Conflicts:
	src/Oro/Bundle/CalendarBundle/Migrations/Schema/OroCalendarBundleInstaller.php
BAP-5251: System and User Calendars
BAP-5985: Add SystemCalendar entity;
- added unit tests
BAP-5985: Add SystemCalendar entity;
- added backgroundColor attribute
Merge pull request #3175 from laboro/ticket/BAP-5985

BAP-5985: Add SystemCalendar entity;
Merge branch 'feature/BAP-5251' into ticket/BAP-5988
BAP-5988: Add system calendars to System navigation menu
Merge pull request #3166 from laboro/ticket/BAP-5988

BAP-5988: Add system calendars to System navigation menu
Merge branch 'master' into feature/BAP-5251