OBEX: Support BTOBEX lib.

Add javax.btobex lib to support Obex Over L2CAP
features in further steps.

Add base files from AOSP OBEX lib to btobex folder
at frameworks/base/btobex project for now.

CRs-Fixed: 639499
Change-Id: I983830bce32fbd1446500b9656978e090ca9f259