Suggest optimal configuration and safe guards

[knoguchi]

When you allocate roles to the servers. the wizard should recommend values. When ever configuration is updated, it should check new values does not break the operation.

• List up critical configuration keys and formula.
• Prioritize them
• Implement

Example:

• total num of threads of the all roles for the host < cores of the host
• max direct memory + heap should > XXX * num of threads. XXX differs for roles. The role would fail to start otherwise.
• the total number of peons * max heap + direct memory < total RAM.