Docstring injector

[germa89]

Ideally we should have a way to inject information in the doc strings of functions we wrap.

Context

There are multiple versions of MAPDL (v23.1; ... v22.1). Most of the functions do not change between versions, but there are some of them which get new documentation. The documentation parsing issue is going to be fixed in #774 and #874 issues. However, versioning will be still and issue, further more, we also change the functions inputs and documentation in PyMAPDL implementation. In order to have matching documentation across MAPDL versions, and PyMAPDL versions, we need to be very careful and thoughtful about how to implement changes. Moreover, there are some talks about how documentation versioning should be done. Currently we are using sphinx with only one final version, but we should probably use readthedocs to have consistent document versioning.

Approach

This PR is going to heavily depend on the results of #774 and #874.

Limitations:

• Injecting the docstring only works for help command, it does not work for sphinx.

[germa89]

To add docstrings to #976 new keywords.

[germa89]

This might be replaced or maybe it will complement #874 and #774 when we start to work with the XML.

[germa89]

Injecting the docstring does not work with the current sphinx configuration.