add example bp handler code to check calling stack frame
create new java_bridge classes: jobject, jclass, jarray, jthread, jmethod_id, jfield_id, jmonitor
include a traceback function when calling Lua cb_breakpoint() from jvmti event handler
lj_get_method_id() now requires a class instead of just a class name
fixed jfield/jmethod listing on classes to not free jvmti refs unless some were found

need to be done to complete this:
  allow jmonitor to create a new object without a raw pointer
  reduce (and eventually eliminate) use of lj_* everywhere outside of java bridge
  check if its possible to disallow class=nil being passed to jmethod_id.create()
  fixup dump() debug function
  make event_queue.lua a more "proper" module, and its use in jthread.lua
  write jarray.__tostring and .__eq
  default jobject.__eq to use reference comparison via jni
  try to find better places to consolidate the functions in java_bridge.lua
  rework argument handling in jcallable_method
  rename all classes to start with uppercase letters
  finish poseidon docs for new classes
  write docs for how jobject works and how to subclass it
  access force_early_return from frame/thread or w/e