Add validation for cache model

[marki1an]

My proposal validates the cache model.

Was configuring for single-node Redis.

 spring:
   redis:   
     host: host
     timeout: value
     port: value

spring:
  redis:
    cluster:
      nodes:
        - host_1:port_1
        - host_2:port_2
        - host_3:port_3
    timeout: 300

Actual for a single-node

 spring:
   redis:  
      single-node:    
        host: host
        timeout: value
        port: value

and for cluster

 spring:
   redis:  
      cluster:    
         nodes:
          - host_1:port_1
          - host_2:port_2
          - host_3:port_3
         timeout: 300

[And1sS]

Why not simple @ConditionOnExpression? Just to make it look cleaner?

[marki1an]

Corresponding PR : #63