Moved to single speaker json

/src/org/osuosl/ocw/Schedule.java: Changed url to root + speakers.json. All speakers are not loaded into memory on launch so are always available through the variable mSpeakers. Changed some speaker initialisations form null to new Speaker(). When a speaker isn't found in mSpeakers a force load of speakers is performed. loadBio now loadSpeakers and now returns void and receives parameters, loads all speakers either from database or json under the same circumstances as before.