Pre-release of 1.0.10 with different proxy implementation

Changes the implementation and configuration for proxy support. The proxy is now configured in one place similarly to the New Relic .NET Agent:

<!-- Proxy settings for connecting to the New Relic service. -->
<!-- If a proxy is used, the host attribute is required.

    Attributes:
    host - The proxy server host name.
    port - The proxy server port (optional - defaults to 8080).
    user - The username used to authenticate with the proxy server (optional).
    password - The password used to authenticate with the proxy server (optional).
    domain - The domain used to authenticate with the proxy server (optional).
    useDefaultCredentials - 'true' or 'false. Uses the credentials of the account running the plugin (optional - defaults to false).
                            If specified, 'user' and 'password' are ignored.
-->

<!--
<proxy host="hostname" />
-->