Workflows for relax md runs

[JPchico]

Adding dedicated workflows for structural relaxation via the minimize option from lammps and a dedicated md workflow. These should replace what the deprecated calculations did in a more flexible manner. It is still possible to set all kinds of fixes, computes, etc as one would for the base workchain.

The underlying base workchain is still controlled via the parameters entry port, the difference is that its values are set via dedicated input ports, they are validated to make sure that they make sense in their respective contexts.

@chrisjsewell , @sphuber let me know what you think. I still need to add the tests and documentation.

[codecov[bot]]

Codecov Report

Merging #85 (0e872ec) into develop (5f56b29) will decrease coverage by 0.69%. The diff coverage is 81.37%.

@@             Coverage Diff             @@
##           develop      #85      +/-   ##
===========================================
- Coverage    85.98%   85.30%   -0.69%     
===========================================
  Files           17       19       +2     
  Lines         1356     1599     +243     
===========================================
+ Hits          1166     1364     +198     
- Misses         190      235      +45     

Flag	Coverage Δ
pytests	85.30% <81.37%> (-0.69%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
aiida_lammps/workflows/md.py	72.00% <72.00%> (ø)
aiida_lammps/workflows/relax.py	85.11% <85.11%> (ø)
aiida_lammps/calculations/base.py	96.62% <100.00%> (ø)

... and 1 file with indirect coverage changes

[JPchico]

@chrisjsewell , @sphuber

Here are some basic workchains the user can now use, one basic for relaxation and another one for md runs. I added some basic testing to them and I plan to add documentation in the documentation revamp that I'll do in another PR.

Let me know if you think this is okay, or if there be more changes.

Cheers

[chrisjsewell]

looking great cheers