GOPROXY is used to download packages from fastest source,
disable it will let all packages download from github.com

By default Beremiz' runtime needs a staticly compiled open62541 library but the component one by default produces a shared one. Thus explicitly request it with BUILD_SHARED_LIBS=OFF flag.

fixes TypeError: cannot marshal <class 'dict_keys'> objects

See merge request !1250

this is the default

mostly packages with known vulnerabilities or causing failures/warnings
in the tests.

This also cleanup duplicates version definitions, sometimes the test
profiles overloaded some versions from stack/slapos.cfg

this is not used here and pulls many dependencies that we don't need

"image" is something else which depends on pillow, but also django,
which we don't need here.

This is a fixup of 99d9c776

This way of forcing python3.7 is better because the name of the part is
still "python3" hence in the package we have

/opt/slapos/parts/python3/bin/python3

instead of

/opt/slapos/parts/python3.7/bin/python3

See merge request !1249

software.cfg becomes python 3
software-py3.cfg no longer exists
software-py2.cfg is introduced

Test suites will have to be updated accordingly

default profile no longer exist, now we have a combination of explicit
zodb versions and python versions:

{zodb4,zodb4-wc2,zodb5} x {py2,py3}