Add a Time interface should automatically select last used project

[conorsmith]

To reduce the amount of clicking a user has to do the Project select element should automatically set itself to the last project the user added a time for. Can be achieved with a method on Model_Member like this:

$member->get_last_added_project()

For users such as myself that log their time for a project in small chunks over the course of the day, this will reduce a lot of clicking.

For users that jump between projects with every addition of time it will make little difference to their actions compared to the current situation.