initial check in for guage support
Merge branch 'develop' of github.com:caskdata/cdap into feature/metrics-guage-support
 removing explicit  Metrics content type {count,gauge} instead, we will allow user to call gauge or increment the metric value based on the use-case
reomove unwanted formatting changes
refactor set to gauge
 test case for gauge
remving irrlevant comments
adding enum metrics type for count and type and recording them in Metrics Record and changing behavior in collection service
adding gauge for user metrics
removed a todo
doc and format fixes
updating metric name to be relevant
cast to long in mapreduce metrics emitter instead of int
minor comments and name fixes
renamed variable to be consistent
 renaming interface MetricType to MetricCategory
renamed MetricContentType to MetricType
renaming COUNT to COUNTER in MetricType and other minor changes -- code review
revert back rejectedExecutionHandler to use increment instead of gauge
Merge pull request #568 from caskdata/feature/metrics-guage-support

CDAP-484 User and System Metrics Gauge Support