unpacker plugin base class poc

[jstucke]

• Adds a base class for unpacking plugins
  • is backwards compatible with old plugins (in fact only one plugin was converted to the new class as PoC)
  • makes boilerplate code at the end of plugins unnecessary
• fixed a bug in the Xiaomi HDR and generic_carver plugins
  • the deactivated logging in the carver broke the logging output of the HDR unpacker
  • added log capturing to the generic carver instead (the same way it is implemented in the HDR unpacker)
• analogous to Remove pluginbase FACT_core#985