Added Activity-Object, so that Activities can be handled (just the ID at
the moment)
Added Kimai_Database_Mysql::getActivities, wich will return
an Array of Activity-Instances
Added Activity::Name, so you can save the Activities Name
Added Activity::Visible, so you can handle the Visibility of an Activity
Added Activity::Comment, so you can handle the Activitys Comment
Added <br> after showing an Object in dev.objects, so the amount of
Objects is better visualized
Added Activity::Deleted, so you can handle the Deletion-State of an
Activity
Added Activity::Budget, Activity::Approved, Activity::Effort, these
Values are optional
Added Kimai_Database_Mysql::getActivitiesForProject, so you can load
Project-specific activities with their budgets
Kimai::getActivities can optionaly get an Project-Argument, so the
returned Activities will be for this Project, they wont be cached
Added Project::Activities, so you can get the Projects Activities
through an property. They load just once, than they will be cached