Allow the agent to be configured with package name / classloader restricts

[mikehearn]

Our app uses fibers in a small part of its codebase, including classes loaded via a custom classloader. But the rest of the app (>10,000 classes by the time it's started up, d'oh) doesn't need them.

Unfortunately Quasar scans all loaded classes, and this significantly increases startup time. Without the agent, the server starts in about 2.5 seconds. With the agent, it's more like 4.5-5.0 seconds. So, nearly double the time.

It'd be nice if we could inform the agent about where to look so it can skip the majority of the loaded classes. For instance, by specifying ProtectionDomains (i.e. jars) to scan, or alternatively, package name wildcards to not scan.

[pron]

In SNAPSHOT. To exclude packages, add exclusion patters separated by ; as agent parameters like so: `-javaagent:=x(pattern1;pattern2;...)

[mikehearn]

Sorry for taking so long to get around to really exercising this feature.

Here are some startup timings. Without exclude pattern:

[18.829425, 13.800646, 13.932261, 14.451902, 18.473767, 13.772951, 18.821028, 13.446343, 18.580407, 14.966181]

After we wrote a tool to calculate some exclude patterns and apply them:

[8.154252, 9.509119, 6.668626, 6.723968, 6.70011, 6.691607, 7.034623, 6.689348, 7.492139, 7.320871]

Pretty nice improvement! The exclude patterns are kind of ugly/hacky - perhaps a way to tag classloaders with include/exclude flags would be nicer, but it works.

Can you do a release with this included? We'd rather not depend on a snapshot.

@exFalso

[pron]

I'll do a sweep of open bugs that can be fixed quickly and cut a release next week.