Homogeneization of start methods enabling start(Endpoint) on all session types
- HttpContentSession provides
-- start(contentPath)
-- start(repositoryItem)
-- start(HttpEndpoint)
- SdpContentSession provides
-- start(sourceContentPath, sinkContentPath)
-- start(sourceRepositoryItem, sinkRepositoryItem)
-- start(SdpEndpoint) (specific SdpEndpoint on each sesstion type)

Change-Id: Ia9685617b2463ca133af71fbbc7cf970dfd534cc