addHostAttr(...) signature change Changed the signature of Plugin.addHostAttr from addHostAttr(name, Host, PluginOrConfig, force) to addHostAttr(name, Host, Plugin, setter, force) because it has come up on multiple occasions that I want a trigger attribute to accept other values, and there's little value in having to define the entire attribute config to get that functionality. Also, the boilerplate attribute setter does a fair bit of work that is likely to be missed in recreating the config for each trigger attribute.

Move pluginattr into plugin dir and ammend meta No other module that lives as a "plugin" in the host module's loader meta and builds files into the host module's build directory has its own src directory. So rather than breaking new ground (and probably some code with it), pluginattr can live in the plugin module directory.

Added module-specific loader metadata json files and the script to put them together