Update docs & Added the retrieve function

• Updated Documentation
  • Made it simpler
  • Prepared the detail documentation for Local DB and Tools: https://localdb-docs.readthedocs.io/en/master/
• Added retrieve function Added and confirmed the retrieve function, which can retrieve data from Local DB and
  • Display the test data log in command line
  • Put retrieved data files into local directory
  • Also added the description in localdb.md