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.
Merge pull request #25 from markholland/enhancement-14763

Moved to single speaker json