Shift feature required

[Gavin]

Currently the taskGroup is used as "Electrical Dayshift", "Electrical Nightshift". This should factored out into a Shift table and a task.shift should then be used for this assingment.

When a person logs in they should be able to select their current shift and see only those logs.

class Shift {
    @indexed // Is auto indexing available?
    String ref // A constant used for lookup, e.g: dayshift.
    String name // Language free, e.g: Dayshift, Nightshift.
    String description = ""
    Integer startHour = 0 //24hr format, e.g:06
    Integer startMinute = 0 //24hr format
    Integer finishHour = 0 //24hr format, e.g:18
    Integer finishMinute = 0 //24hr format
    Integer startFinishMarginHour = 2 //margin in hours.
}