Rename "city" entity as "work calendar"

[jaragunde]

trafficstars

The "city" entity actually represents a work calendar. The name is misleading and doesn't reflect the importance it has (e.g. why setting a city for every user is compulsory to have the acc. hours report working).

It should be renamed at every level of the application, although we could start with the frontend.

[jaragunde]

In the frontend, we have two menu entries related with this entity: cities (link to cityManagement.php), to create or delete this entity in particular; and calendar (link to calendarManagement.php), to assign public holidays to a certain city.

My proposal is to leave only the "city" entry in the menu (which will be renamed to "work calendar" eventually), then add a link inside cityManagement.php to access calendarManagement.php.