Issue #222. Breaking API changes to address issue #222.

[alexeyOnGitHub]

        Migration for RedmineManagerFactory:

        * createShortTermConfig(connectionManager) -> getNewHttpClient(connectionManager)
        * createUnauthenticated(String uri, TransportConfiguration config) -> createUnauthenticated(String uri, HttpClient httpClient)
        * similarly for other createXX() methods that required TransportConfiguration - they now work with HttpClient
          directly.

        Other changes to address threading issues:

        * deleted Pooling connections. createConnectionManagerWithExtraTrust(), createDefaultConnectionManager()
         and all similar methods now return ClientConnectionManager instead of PoolingClientConnectionManager.
        * no more shutdown() method in RedmineManager. if you want to close HttpClient connections, do it directly
        on HttpClient you create.
        * no more createShortTermConfig() and createLongTermConfiguration() methods. create your own HttpClient
        instances and pass them to RedmineManagerFactory if you want to control connection pooling, evictions, etc.