* scm/define-music-properties.scm (all-music-properties):

* scm/define-music-properties.scm (all-music-properties):
create-new property.

* lily/context-specced-music-iterator.cc (construct_children):
inspect 'create-new property iso. magical $uniqueContextId context
id.

* lily/parser.yy (optional_id): allow \new "Bar" = "foo" too.

* lily/context-key-manager.cc (Module): new file. Encapsulate
object key generation.

* lily/include/context-key-manager.hh (Module): new file.