fixes gh-370

Should be no change for users of Boot 1.2 right now, but with this
patch it is possible to use 1.3 with the new conventions for metrics
(e.g. in particular exporting by declaring beans of type
MetricWriter)

fixes gh-353

fixes gh-347

fixes gh-348

 fixes gh-350

fixes gh-341

Fixed a typo in the doc

fixes gh-328

Reason why Eureka instance is not found, is not visible

Make creation of the RestClient LAZY as it is no always required (issue #312)

With the following configuration at `bootstrap.yaml`

```yaml

spring:
  application.name: spring-cloud-hystrix-dashboard
  profiles.active: prod
  cloud:
    config:
      discovery:
        enabled: true
        serviceId: spring-cloud-server-config-with-eureka
server.port: 9003

turbine:
  appConfig: some-service
  clusterNameExpression: 'default'
```

I wasn't able to see why Turbine can't find the instance. The reason was related to SPEL:

```
org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 0): Property or field 'default' cannot be found on object of type 'com.netflix.appinfo.InstanceInfo' - maybe not public?
```

Anyways there was nothing there in the logs so maybe it should not be silenced like right now?

fixes gh-324

fixes gh-325

fixes gh-323

https://github.com/spring-cloud/spring-cloud-netflix/issues/312)

fixes gh-307

fixes 305