v0.6.0

• Add XXXBuilder to help modify class-bound object (no need for struct-bound object), you can write let xx = XXBuilder(x); xx.key = value; xx.build() like you would in Obj-C. It is not Swifty, but useful to avoid some class of errors.
• Relax condition on workspace.dictionary so as long as workspace is mutable, you can now write workspace.dictionary["somekey"] = somevalue, this feels more ergonomic.
• Update flatbuffers dependency to latest.
• Add support to move to "ROLLBACK" again, and potentially vacuum. This helps if you want to use the result SQLite file as a single-file and move it around.
• Support observation for dictionary, so you can workspace.dictionary.subscribe("key") { update in ... }. There could still be some ergonomic improvements, but this helps your code to be more streamlined (i.e. having UI update all derived from observation).