Enable dict style entry in dashboard/*.py

Make dashboard more readable: support "description" instead of query string.

Enable these styles:
( dashboard/cpu.py )
1. only string:
queries = [
    'plugin=cpu type=user group by server',
    'plugin=cpu type=system group by server'
]
 
2. string and dict:
queries = [
    'plugin=cpu type=user group by server',
    {  
        'query': 'plugin=cpu type=system group by server',
        'description' : 'cpu system'
    }
]

3. all are dict:
queries = [
    {  
        'query': 'plugin=cpu type=user group by server',
        'description' : 'cpu user'
    },
    {  
        'query': 'plugin=cpu type=system group by server',
        'description' : 'cpu system'
    }
]