Decode algorithm prototype content if python is older than 3.6

Closes #71

See merge request !61

Fixes #71

ZMQ architecture documentation

Closes #70

See merge request !60

The some of the commands described here were for the V1 API.

Move license to BSD 3 Clause

Closes #60

See merge request !59

Fixes #60

Worker: decode recieved job data if python older than 3.6

See merge request !58

Prior to 3.6 the json module handles only str types. After that
more types are supported out of the box.

Fix docker-pull implementation

See merge request !57

[test][test_docker] Increase a bit more the container memory for the memory-limit test (maybe a py3 requirement?)

This commit resets the container memory limit on the memory-limit test
to a higher value.  It turns out that Docker-18.09 is complaining it
cannot set the memory of the container in question to 4 Mb, possibly
because it starts up with more than that memory already (see discussion
about this here:
https://unix.stackexchange.com/questions/412040/cgroups-memory-limit-write-error-device-or-resource-busy).  Increasing the container memory to 10 Mb
and to the allocated array to 20 Mb makes the test work again.