Add graphs of Java (JVM)

Fetch JMX metrics using Jolokia and draw following graphs:

- Ledge
    - start date
    - JVM name, version and vendor
    - name of garbage collector
    - parameters
- Graph
    - number of loaded class
    - number of total and daemon threads
    - number of young generation and full GC
    - elapsed time of young generation and full GC
    - total heap memory usage (max, committed, used)
    - total non-heap memory usage (max, committed, used)
    - memory usage of Eden in new area (max, committed, used)
    - memory usage of Survivor in new area (max, committed, used)
    - memory usage of old area (max, committed, used)
    - memory usage of permanent area (max, committed, used)
Merge pull request #43 from hirose31/feature/jvm

Add graphs of Java (JVM)
Fetch only once even if that host exists several times in server_list.yaml
Allow same "label" in one "servers"
Merge pull request #44 from hirose31/feature/squash-dup-host

Fetch only once even if that host exists several times in server_list.yaml
Merge pull request #45 from hirose31/feature/squash-dup-label

Allow same "label" in one "servers"