Make some master configuration properties dynamically configurable

This commit adds the ability to change some Master parameters dynamically. Thus, you can enter a web console and change these parameters while the Master is running. These parameters include:

1. millisToWaitBeforeDeleting - time to wait before dropping a segment from a server.
2. mergeBytesLimit - The maximum number of bytes allowed during a segment merge.
3. mergeSegmentsLimit - The maximum number of segments that can be merged together.
4. maxSegmentsToMove - The max number of segments the master moves on each run.

The web console interface is accessible from [serveraddress]/static/dynamicConfigs.html