* Stats: Improve Frequency, enable coalescing; cleanup and javadocs

...console/java/src/net/i2p/router/web/OldConsoleHelper.java

...erconsole/java/src/net/i2p/router/web/StatsGenerator.java

apps/routerconsole/jsp/stats.jsp

core/java/src/net/i2p/stat/Frequency.java

core/java/src/net/i2p/stat/FrequencyStat.java

core/java/src/net/i2p/stat/Rate.java

core/java/src/net/i2p/stat/StatManager.java

router/java/src/net/i2p/router/StatisticsManager.java