DM-996 part 2

Created by: SkyToGround

Description of work

• Build nodes now use GCC8.
• Changed namespace Module into namespace WriterModule.
• The class Module::WriterBase is now instead WriterModule::Base.
• I have split the files HDFWriterModule.* into WriterModuleBase.* and WriterRegistrar.*.
• Added support for (and requirement of) module names into the writer registration code.
• Added/changed unit tests for new writer module registration code.

Nominate for Group Code Review

• Nominate for code review