Separate class for main function and controller

Public main function in LDo class and Controller in a new class.
Added try-catch block in exeuteCommand()
Merge branch 'master' into controller/sharon

Conflicts:
	sg/codengineers/ldo/controller/LDo.java
Cancelled try-catch block
Run shows welcome message and today's task list

When L'Do is run, it will show a welcome message and today's task list.