draft: Note no longer carry field title

[neo451]

I realized need to make these more radical changes early, or else other refactors can not move forward, and people need time to adopt.

Idea at #412

Implication:

1. No longer insert title as header 1
2. Note class and creation API is easier to understand

changlog:

• added default note_path_func in config values

TODO:

• Tell or offer how to insert a heading on note creation like old behavior, add a link in the wiki, put it in breaking changes
• direct user input "id" to template subistitution {{title}}???
• default note_path_func and note_id_func should have same signature
• note.path_func
• note.id_func