Add hostame or version as resource to plugin settings

[wrooot]

Spark already have Hostname as Resources and Version as Resource settings in default.properties file, so one can hardcode this. But it would be more convenient for admins to set these settings via Admin Console.

As only one can be true, currently Hostname is used when both settings have value "true". Ideally one of the settings in the list should get disabled when another is selected. Though it might be harder for me to implement (for now a note in description should work).

[wrooot]

On Spark end it is implemented via https://issues.igniterealtime.org/browse/SPARK-2086

[wrooot]

I've messed up while trying to clean my history and commited directly to ignite repo instead of my fork. Wanted first to show my PR to someone, but, whatever.

There is a small issue though. Two added settings are not changing on a first save. One have to change setting and press Save again for them to stick. Probably related to my wish to make them disabled by default. First of all they won't work along and also some users might want to have their custom resources and this will change if admin updates Client Control plugin.

[wrooot]

Another nice to have option would be to disable one option, when another is set to Enabled (as they can't be both enabled).

[wrooot]

Have decided to make these settings enabled by default (this way saving them works fine). Probably not a big deal that both will be enabled and Hostname will be used as a resource once admins update the plugin. Leaving it for someone else to figure out how to make them disabled by default or how to block one when another is enabled.