Project selection filter on iOS. Re: Issue #111.

A quick implementation of a project selection screen filter for iOS.

* Filter-as-you-type.
* Filters by project name and task name.
* Hides “No project” and “Create new project” while filtering.
* Shows all workspaces while filtering.
* Does *not* filter by client name, yet. Getting client names from outside a data view turned out to be tricky.
* Shows and hides the Cancel button automagically.