Added drag & drop via react-dnd

[Davidster]

related to issue #45. Sorry but this will be a lazy PR description.

Summary

• Added the ability to move courses around the sequence via drag and drop. OrLists are non-draggable.
• Added the ability to add new courses into the sequence. This was done by adding a CourseItem box into the course info panel when a new course is searched for. You drag the course into the table to add it.
• Including the two above cases, you can never drag a course into a semester which already contains that course. You can, however, have more than one instance of a course in the entire sequence as long as they're in different semesters (recall that the 490 level courses span two semesters)
• Added the ability to remove courses from the sequence. This was done by adding a garbage can icon which pops up in place of "Conu Course Planner" whenever you start dragging one of the courses in the sequence. You drag the course into the garbage can to remove it.

As you know, react-dnd was used for these changes. The code will probably look pretty trippy. Using these higher-order components is interesting...

Test

http://138.197.6.26/courseplannerd/ - remember that you can reset the sequence to default by selecting a new program from the drop down menu.

[Davidster]

There is a bug with this PR - select an item from an orList and then click on the course, you get an error: Uncaught TypeError: this.props.onOrCourseClick is not a function. Will fix when I get back from vacay

[Davidster]

In my most recent commit I fixed the bug I mentioned and added the requested change.

Please test: http://138.197.6.26/courseplannerd/