Direct links database

Make some changes to let all opening functions can adopt new behavior.

1. add new global variable `dirty` to leave `config` in a clean state
2. no additional argument for `$.openLink`, that should be internal
3. `bypassWithServer` stores a function, to use different open handler
4. I don't know why you overwrite `identifier` again, but I have simplified the stripping. BTW, I think leading slash does not need to be stripped.