adds custom parameters for loadbalancer

Adds the ability to send custom parameters to the external
loadbalancer. When fetching the status is adds the custom
parameters to the query string. E.g. if the custom parameter
is called host and has a value test then then the url will be:

http://theloadbalancerurl/server-status?name=test&host=test

The new option is called LoadBalancerParameters and is nested
under the Agents node.

"Agents": {
	testagent1": { "LoadBalancerParameters": { "Host": "testgroup1" } },
Adds regex matching with ranges on agent names

Adds regex ranges to the agent names in the config
file. Asterisk wildcard existed already, this allows matching
agents using a range.

E.g. test[1-4] matches test1, test2, test3 and test4.

Example from config file:

"Agents": {
        "testagent[1-3]": { "Environment" : "test1" },
        "testagent[4-6]": { "Environment" : "test2" }
}
Merge pull request #10 from asimov-deploy/loadbalancer_custom_params

Custom parameters for Loadbalancer integration