[Feature] Error handling

[ezpzbz]

[Feature] Error handling

[ezpzbz]

I've tried different ways to implement the error handlers (keeping in mind to avoid changes in plugin), however, it is inevitable at the end. The final solution that I came up with is as follows:

• Get the list of possible errors from cusodian
• Define different exit codes for them in aiida-vasp plugin.
• Parse errors in workchain: these can be parsed from _scheduler.stdout, _scheduler.stderr, and vasprun.xml
• Connect parsed errors to relevant exit codes. It needs to be done in VaspBaseWorkChain.
• Call proper handler in VaspBaseWorkChain to fix the issue.