Draft: More flexible command handling

Multiple changes:

• Allow not having a [parallel] section
• Remove the parallel boolean in general
• Rename ArgvProfile to StandardProfile since this name seems more communicative, covering many cases
• Remove .name attribute on StandardProfile
• Enable "extended" interpolation in configparser so we can do thing = ${otherthing}
• BaseProfile and derivatives have self.binary now along with self.command, which is intended to be a template based on the binary. Right now the only template substitutions are done at the configparser level. ConfigParser interpolation has been enabled so one can do ${var} which seems to be the nicer alternative to the somewhat non-standard %(var)s syntax.
• Add "configvars" attributes to profiles which is a way to specify statically what strings are expected. This means e.g. Siesta can have pseudopotential paths and DFTB can have skt_path.
• Remove the old boolean from Onetep which apparently doesn't do anything that we cannot do by preprocessing the command
• Add configurable parameters for pseudopotentials etc. where appropriate
• Move the binary attribute to BaseProfile rather than all the implementations

Closes #1468, #1392, #1292.

Checklist

• I am familiar with ASE's contribution guidelines.
• Doc strings in code changed in this MR are up to date.
• Unit tests have been added for new or changed code.
• Issue is resolved via "closes #XXXX" if applicable.