[Feature] Moving to aiida-core BaseRestartWorkChain

[ezpzbz]

Currently, we are using the BaseRestartWorkchain from aiida-vasp plugin. It is the implementation that was introduced in aiida-quantumespresso at the first place and then started to being used in every plugin. However, as it was quite useful, AiiDA team has moved it to the aiida-core and improved it by adding nice error handling mechanism. Therefore, it is a good idea that we also start using it in our workchain. It requires:

• Carefull reading the plugin to avoid possible bugs that can be introduced and break the current API
• Implementing it and add at least one error handler to have a starting point
• testing it and making it ready to be merged into master.

[ezpzbz]

These are implemented in base_restart branch. The required error handling stuffs within the workchain need to be impleneted at plugin level. The reason is that we can spot if a subprocess has failed but relating it to the error cannot be done easily at this level.
Thefore, we define the exit codes in plugin, then we have an error parser which acts at workchain level. If it spots subprocess failures, it registers the error code coming from plugin. The handler then acts based on that (again at workchain level)