MusicDataBaseDirectory::NODE_TYPE: convert to enum class

[notspiff]

Description

Rename and change an enum to an enum class

Motivation and context

More modern, more type safe, ..

How has this been tested?

It builds

What is the effect on users?

None

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• Student submission (PR was done for educational purposes and will be treated as such)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• [] My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed

[ksooo]

DirectoryNode.h is included in many header files. Any chance to replace some of the includes with forward declarations to the new enum class now?

Quick check:

• filesystem/MusicdatabaseDirectory/QueryParams.h
• filesystem/VideodatabaseDirectory/QueryParams.h
• filesystem/MusicDatabaseDirectory.h
• filesystem/VideoDatabaseDirectory.h

[notspiff]

added another commit with the forwards. the video ones will have to wait until the PR that changes the video enum (next in my queue..)

[notspiff]

good to go?

[garbear]

LGTM

[ksooo]

Shove it in.