Plugin run on the remote host doesn't load due to CSP

[mmelko]

Because it violates the following Content Security Policy directive: "script-src 'self' 'unsafe-inline' 'unsafe-eval'". Note that 'script-src-elem' was not explicitly set, so 'script-src' is used as a fallback.

How to reproduce:

1. run springboot-plugin example on the different host to host the sample plugin
2. modify SampleSpringBootService in the springboot-plugin example on your host to include URL of remote plugin:
   e.g:

 HawtioPlugin plugin = new HawtioPlugin(
           "samplePlugin",
           "./plugin",
           "http://192.168.1.169:10001");
           ``` 
3. try to load the plugin accessing `http://localhost:10001/actuator/hawtio/sample-plugin` and see the exceptions. 

`Becauseecause it violates the following Content Security Policy directive: "script-src 'self'". Note that 'script-src-elem' was not explicitly set, so 'script-src' is used as a fallback.`
To fix this the host of the plugin has to be added into `connect-src` `script-src` and `style-src` parts of the CSP