Update UiSandboxMain port

Use the default port 4000 to help avoid confusion.
Use glowroot Ticker to avoid shading hassles
Fix ticker usage
Optimize TraceMetric
Finish changing 'metric' to 'trace metric'
Microbenchmarking
Create testing subdirectory
Add commons logging support to logger plugin
Fix checker framework annotations for json binding
Rename a few things
Make thread and gc info capture optional
Microbenchmarking
Optimize TraceMetric and Span

Microbenchmark shows that this reduces trace metric capture overhead
from 88 down to 41 nanoseconds, which is very good since
System.nanoTime() takes 17.5 seconds, and trace metric capture has to
call it twice to calculate duration.
Optimize jdbc plugin
Update README.md
MBeans
Reduce memory footprint of ParsedTypeCache

In particular big impact when thousands of GroovyClassLoaders.
More reduce memory footprint of ParsedTypeCache
Simplify WeavingClassFileTransformer
Simplify AdviceCache