Add back old changelog entries and fix a few markdown formatting issues.
Add back old changelog entries and fix a few markdown formatting issues.

splunk/splunk-sdk-java,dkelmer/splunk-sdk-java,splunk/splunk-sdk-java,dkelmer/splunk-sdk-java,dkelmer/splunk-sdk-java,splunk/splunk-sdk-java,splunk/splunk-sdk-java,dkelmer/splunk-sdk-java,dkelmer/splunk-sdk-java,splunk/splunk-sdk-java,splunk/splunk-sdk-java