java: remove some unused fields in the ODK examples

Change-Id: Ic6b4f18aefba6603af51d17d061e3f821e95261f
java: remove unused import

Change-Id: Ic703b12c864093764f8d213534af1b2496930e79
java: remove various unused variables

Change-Id: Id9f30938f594cb6fe73bf40adfffa65ec1b42cd1
java: remove unused fields

Change-Id: I6c93864f501f646a8940eac221a88c87b3f75525
java: remove commented out code

Change-Id: I44e2043e5da23bc9421c03e550ef1d8b7ebaad36