Publish python package

See merge request ska-telescope/csp-lmc-subelement!6

Included: POGO file, tests and Docker configuration files.
Removed overloading of the adminMode attribute for SubElement
Master and Subarray.
Use of pytest-fork.
Updated release version.
Added HISTORY file to records release changes.

Request to merge AT5-370 branch with master

See merge request ska-telescope/csp-lmc-subelement!5

Changes to docs configuraiton files.

dependencies.

configuration from dsconfig file: if polling is enabled for the attributes,
the test on attribute reading is not performed because the value is read
from the cache and not from the device.
Polling has to be enabled into the dsconfig file when the real
devices are instantiated)

Fixed some bugs in device code.

command execution.

files.
Updated setup.cfg and setup.py.

First release of the sub-element master device.