Fixed case where ibrowse_lb could lose its ETS state table

Replaced all traces of ETS in ibrowse_lb with a dict. This reduces
overall ETS table usage (finite resource) and eliminates the case
where an 'EXIT' message could cause an ibrowse_lb process to delete
its backing ETS table.

State is now tracked using a dict and is passed around as needed.
Made modifications to the stats and metrics API to accommodate the
new tracking mechanism without impacting overall monitoring.

Fix format and remove unreachable code
Bumping vsn to reflect ibrowse_lb fix