calling `merge_config` in `init()` breaks use as a plugin

[cdent]

Because merge_config is called in init() it is very difficult for some other plugin which wants to depend on tiddlywebwiki (e.g. tiddlyspace) to override a configuration setting because:

• tiddlyspace config sets (e.g) tiddlywebwiki.friendlywiki to False in config
• then calls tiddlywebwiki.init(config)
• in there tiddlywebwiki's config is imported and then merged
• friendlywiki setting is now clobbered

Not sure of the right way to fix this. There's a workaround, which is to undo to the code you don't want in the calling plugin. Annoying.

[cdent]

My intention is to rewrite tiddlywebwiki using "modern techniques" (whatever that is) and avoid this situation.

See tiddlywebwiki2 for some old thoughts on the matter.