Search Enhancements

- Paths now can have unicode characters
- Long tap on search result shows book infos
+1 on what chrox said.

@NiLuJe , In fact, we have our own implementaion of round in https://github.com/koreader/koreader/blob/master/frontend/optmath.lua ;) As for unused file handles, theoretically it should be handled by GC. But we have been beaten by it before. So I guess we should avoid relying on GC and free resources manually whenever possble.