hci_dump: add a dump level parameter

Allows the verbosity of the output to be controlled. Levels are, in
increasing order:
    NONE = 0
    ERROR
    INFO
    DEBUG
    PACKET
Any information from above the current level is suppressed. The level
can be set with hci_dump_set_level() and defaults to HCI_DUMP_PACKET for
backwards compatibility.
bnep.h: fix compile error

rename RFCOMM_CHANNEL_STATE_VAR -> BNEP_CHANNEL_STATE_VAR
daemon: allow setting hci_dump log level
add simple .gitignore