Merge pull request #1 from VincentJian/master

JSP + CSS layout
Change to use ZK 6.5.1.1
Add Servlet API
Init business logic.
Upgrade business logic.
* Adjust VO relation
* Split `AbstractDB.java` and `DBProvider.java`
Upgrade AbstractDB:
* add getMilestonesByWorkspace(), getTasksByMilestone()
Fix MockDB.java:
* getMilestonesByWorkspace()
* getTasksByMilestone()
Upgrade structure of Workspace, Milestone and DB interface.
MockDB will generate dummy text to task descript.
implement card view page