changed and added queryTask to logic

-moved queryTask from storage to logic
-replaced methods that used queryTask to call locally instead
added enum for priority
modified setPriorityLevel
added constant for priority

-added message to send when task does not exist when trying to set
priority level
updated priorityLevel in Task
moved queryFreeTimeslots to logic

- refactored it also
modified quertyFreeTimeslots

-added for loop to remove floating tasks
modified queryFreeTimeslots

-added condition to check if task to be added is a floating task
-added condition to check if start time of task is between start and end
time of queried task
-changed method names
-refactored code
Merge remote-tracking branch 'origin/logic'