Fix Javadoc links and update powermock and checkstyle
Fix Javadoc links and update powermock and checkstyle

SpongePowered/SpongeAPI,SpongePowered/SpongeAPI,boomboompower/SpongeAPI,DDoS/SpongeAPI,JBYoshi/SpongeAPI,SpongePowered/SpongeAPI,boomboompower/SpongeAPI,AlphaModder/SpongeAPI,AlphaModder/SpongeAPI,DDoS/SpongeAPI,JBYoshi/SpongeAPI