improve logging and add method entry/exit instrumentation

Here's a first take at some improvements to logging, per discussions with @marco-c in IRC.

This changeset adds the logConsole and logLevel URL params, where logConsole can be any comma-separated combination of *web* (the Web Console), *page* (the in-page console), and *native* (the native console, i.e. *dump*); and logLevel can be any of the values *trace*, *log*, *info*, *warn*, *error* (in that order of severity). Messages at or above the specified log level will be logged to the specified consoles.

I also went through the various `console.*` calls and changed their severities where appropriate. And I added a primitive mechanism to instrument method entry/exit, so we can log within non-native methods without having to modify their Java source. I'd like to add some tests, although I'm not yet sure how to implement them.

Ok, I implemented that strategy. Now the logging looks something like this (including lines logged before and after the SSL logging):

```
I warning: Connection.checkSecurity(S)V commented out (…)
I SSL Output:
GET /…
User-Agent: …
Host: …
Connection: …


I SSL Input:
HTTP/1.1 200 OK
Connection: close
Server: …
Date: Tue, 09 Sep 2014 21:58:22 GMT
Content-Length: 65
Content-Type: text/json ; charset=utf-8

{…}
W DisplayDevice.refresh0.(IIIIII)V not implemented (1, 335544321, 0, 177, 228, 302)
```