build: Add obexctl command line client

obexctl is intended to be a command line client of obexd.
tools/obexctl: Add initial code

This add initial code for things like input handling as well as some
basic commands.
tools/obexctl: Add proxy handling for org.bluez.obex.Session1

This adds proxy handling for org.bluez.obex.Session1 so changes to the
proxy are printed in the output.
tools/obexctl: Add proxy handling for org.bluez.obex.Transfer1

This adds proxy handling for org.bluez.obex.Transfer1 so changes to the
proxy are printed in the output.
tools/obexctl: Add proxy handling for org.bluez.obex.Client1

This adds proxy handling for org.bluez.obex.Client1 so changes to the
proxy are printed in the output.
tools/obexctl: Add connect command

Add support for connect command which can be used to create a session to
a device.
tools/obexctl: Add disconnect command

Add support for disconnect command which can be used to disconnect
sessions.
tools/obexctl: Add list command

Add support for list command which can be used to list available sessions
tools/obexctl: Add show command

Add support for show command which can be used to show session
information
tools/obexctl: Add select command

Add support for select command which can be used to set the default
session
tools/obexctl: Add info command

Add support for info command which can be used to print transfer
information
tools/obexctl: Add cancel command

Add support for cance command which can be used to cancel ongoing
transfers
tools/obexctl: Add proxy handling for org.bluez.obex.ObjectPush1

This adds proxy handling for org.bluez.obex.ObjectPush1 so changes to the
proxy are printed in the output.
tools/obexctl: Add send command

Add support for send command which can be used to send a file using
ObjectPush interface
tools/obexctl: Add proxy handling for org.bluez.obex.FileTransfer1

This adds proxy handling for org.bluez.obex.FileTransfer1 so changes to
the proxy are printed in the output.
tools/obexctl: Add cd command

Add support for cd command which can be used to change current directory
using FileTransfer interface.
tools/obexctl: Add ls command

Add support for ls command which can be used to list current folder
using FileTransfer interface.
tools/obexctl: Add cp command

Add support for cp command which can be used to copy files from/to current
folder using FileTransfer interface.
tools/obexctl: Add mv command

Add support for mv command which can be used to move files using
FileTransfer interface.
tools/obexctl: Add rm command

Add support for rm command which can be used to delete files using
FileTransfer interface.