Add HomeScreenImage to models and db

git-svn-id: svn://192.168.5.211:9188/trunk@300 bb20246c-724e-4bba-9fa3-4b8641970e91
Use better way to make sure time difference is within 1 millisecond

git-svn-id: svn://192.168.5.211:9188/trunk@301 bb20246c-724e-4bba-9fa3-4b8641970e91
Fix bug in handling taskachievement (wrong table name)

git-svn-id: svn://192.168.5.211:9188/trunk@302 bb20246c-724e-4bba-9fa3-4b8641970e91
Add set_click() to HomeScreenImage to record user's click

git-svn-id: svn://192.168.5.211:9188/trunk@303 bb20246c-724e-4bba-9fa3-4b8641970e91