Document service calls for com.palm.lunastats

- Document getMemoryStatus, dumpHeapProfile
- Remove getStats, gc, getAppEvents, enablePiranhaFpsCounter,
  dumpRenderTree, dumpCompositedTree, as the support functions
  for these are not available in standard WebKit.

[GF-6398] Document APIs in com.palm.lunastats

Open-webOS-DCO-1.0-Signed-off-by: Eric Blade <eric.blade@lge.com>

Change-Id: I7ebcdd72da772c872abd6bd7a4220047401888a2