added code to re-create tasksById after load; uncommented code in broken tests
fixed reference to renamed taskstore.js
added missing ajax-loader.gif
converted to two pages - one for task lists and one for tasks
a few new features, and a bunch of bug fixes
added functions to handle lists of task lists
Merge branch '7_pages_and_theme' of github.com:scs-cs-50/task-app into 7_pages_and_theme