can view list of tasks for a specific time range
created method to retrieve all tasks as one list
added method to check if a task falls within a given range of start and end dates
changed view method to be compatible with the new data structure.
changed addTask to be compatible with new data Structure
make delete task compatible with new data structure
removed deprecated methods and variables from Basic Data Handler
Merge branch 'master' of https://github.com/cs2103aug2014-t17-2J/main into NewDataStructure