XD-941: Apply CP to Gemfire, twitter and splunk

~~Note that splunk module is buggy if using auth. You can manually switch the splunk.jar or use a debugger and set Service.token field to e.g. "" to have it working (see https://github.com/spring-projects/spring-integration-extensions/issues/59)~~

* Also moved twitter.properties to twitter.properties.template so that we don't accidentally commit keys.
* Also removed projects from settings.gradle where they're no longer used (and would create ghost projects when running gradle eclipse)
* Also enabled fixedDelay as a parameter to twitter module, as documented on wiki