Code cleanup and data restructure

[jthrilly]

Several elements of the app are poorly structured and need reconsidering.

• The app should not fail if no database connection can be made. The database is not required for typical operation.
• Edges are stored in a pretty stupid way. Instead of $edge_array["$id1, $id2"] we should do $edge_array[$edge_id]['source'] = $uid1; $edge_array[$edge_id]['target'] = $uid2;
• error handling must be revamped. See: Error Reporting #6
• We should reconsider the steps of the app. We should ask for all data in the first step and then not require any further user input until the end. Clicking "download" at each step is laborious and silly.
• Each step should be a self-contained implementation of a function or class. We shouldn't have any dependancies in the step files themselves that aren't met automatically at the time our backend functions are called. For example, each step should provide a callback function to update a statusbar element with text and a percentage of completeness. It should requite everything it needs (friend_list or edge_array etc.) to be passed to it, and not derive this data itself.