Forbid leading, duplicated and trailing dots in field names

Forbid leading, duplicated and trailing dots in field names

In order to simplify the display filter scanner, try to restrict the use
of dots ('.') in field names. Forbid leading dots, does not affect
current dissectors. Fix '..' typo in fpp dissector and forbid it. Forbid
trailing dots after fixing dissectors: some of them just have an excess
dot, others are missing a name after the dot.

Change-Id: I6e58a04ef0306ee8c16fbf6a3cabb076d7fc69c9
Reviewed-on: https://code.wireshark.org/review/26967
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>