all: remove explicit versions in USES=python for "3.x+"

The logic in USES=python will automatically convert this to 3.8+ by
itself.

Adjust two ports that only had Python 3.7 mentioned but build fine
on Python 3.8 too.

finance/quickfix: mark BROKEN with PYTHON

libtool: compile:  c++ -DHAVE_CONFIG_H -I. -I../.. -I -I. -I.. -I../.. -I../C++
-DLIBICONV_PLUG -DPYTHON_MAJOR_VERSION=3 -Wno-unused-variable
-Wno-maybe-uninitialized -O2 -pipe -DLIBICONV_PLUG -fstack-protector-strong
-fno-strict-aliasing -DLIBICONV_PLUG -Wall -ansi
-Wno-unused-command-line-argument -Wpointer-arith -Wwrite-strings
-Wno-overloaded-virtual -Wno-deprecated-declarations -Wno-deprecated -std=c++0x
-MT _quickfix_la-QuickfixPython.lo -MD -MP -MF
.deps/_quickfix_la-QuickfixPython.Tpo -c QuickfixPython.cpp  -fPIC -DPIC -o
.libs/_quickfix_la-QuickfixPython.o
warning: unknown warning option '-Wno-maybe-uninitialized'; did you mean
'-Wno-uninitialized'? [-Wunknown-warning-option]
QuickfixPython.cpp:175:11: fatal error: 'Python.h' file not found
          ^~~~~~~~~~
1 warning and 1 error generated.

Reviewed by:	portmgr, vishwin, yuri
Differential Revision:	<https://reviews.freebsd.org/D40568>

*: Bump PORTREVISIONs for math/mpc update to 1.3.1

Remove WWW entries moved into port Makefiles

Commit b7f05445c00f has added WWW entries to port Makefiles based on
WWW: lines in pkg-descr files.

This commit removes the WWW: lines of moved-over URLs from these
pkg-descr files.

Approved by:		portmgr (tcberner)

Add WWW entries to port Makefiles

It has been common practice to have one or more URLs at the end of the
ports' pkg-descr files, one per line and prefixed with "WWW:". These
URLs should point at a project website or other relevant resources.

Access to these URLs required processing of the pkg-descr files, and
they have often become stale over time. If more than one such URL was
present in a pkg-descr file, only the first one was tarnsfered into
the port INDEX, but for many ports only the last line did contain the
port specific URL to further information.

There have been several proposals to make a project URL available as
a macro in the ports' Makefiles, over time.

One more small cleanup, forgotten yesterday.
Reported by:	lwhsu

Remove # $FreeBSD$ from Makefiles.

Follow up on graphics/py-pillow6 port removal in r559976

The graphics/py-pillow6 port was removed in r559976 as it was for
Python 2.7 only and no longer referenced in the default cases.
However it was still defined in Mk/Uses/python.mk in PY_PILLOW,
leaving a dangling reference.

Remove it from Mk/Uses/python.mk, leaving only the Python 3
version of that port, graphics/py-pillow, defined and bump the
minimal verion of Python to 3.6 for affected ports.

misc/mmdnn: Update 0.3.0 -> 0.3.1

Reported by:	portscout

misc/mmdnn: Update 0.2.5-21 -> 0.3.0

Reported by:	portscout

Convert the tree to use PY_PILLOW

With hat:	portmgr
Originally submitted by:	kai

graphics/py-pillow: Update to 7.0.0

* Repo-Copy the Pillow 6.2.2 release to graphics/py-pillow6 to retain
  backwards compatibility for Python 2 consumers as the Pillow 7.0.0 release
  dropped the support for Python 2.

* Apply conditional statements to use either Pillow 7.x or Pillow 6.x for
  consumers that can be built for Python 2 or newer.

* Exceptions are ports that can be built only for either Python 2 or
  Python 3.  For the first case, consumers are just assigned to the
  repo-copied graphics/py-pillow6.

* Also remove Pillow from BUILD_DEPENDS of math/py-PyWavelets as it is not
  listed in setup.py as a build dependency [1] and relax the version

New port: misc/mmdnn: Tools to inter-operate among different deep learning
frameworks