They should be only Billable and Overhead.
* Hard coded the options for the Billable select instead of dynamically
pull the values from the Custom Field
* Removed TimeEntryActivity#find_with_billable_values in favor of two new
methods to return a TimeEntryActivity if it is billable or overhead.
`find_billable_activities` and `find_overhead_activities`
* Reworked the TimesheetController hook to use the new methods for finding the
TimeEntryActivities
* Updated RSpec examples
Eric Davis