Added Google Direction api and route draw on map

1. Added Google Direction Api to calculate path between source (current
location) and destination (selected destination in list)
2. Added support of showing path on Google Map between source and
destination for walking mode.
3. Required JSON, Async task for communication and various background
task implementation to support the calculation of various details like
distance, duration, paths etc between source and destination.
4. Code cleanup - removed extra methods (not required with new
implementation)