Address review comments.

Convert Ruby snake_case to camelCase.
Handle -Dproperty switches without following "=".
Better method names PidFile.indicateStarting() and .indicateRunning().
PidFile.indicateStarting() throws AlreadyRunningException instead of returning non-negative value.
Fix typo and improve readability.
Document the locking protocol.
Address review comments

Rename Porting to Processes
Fix string incorrectly changed by refactor
Static import checkNotNull()
Minor renaming