Added config option to set the number of acceptor threads used by Jetty. Acceptor threads are those threads dedicated to accepting incoming connections. Increasing the number of acceptor threads can increase the throughput of a running system.

Changes were applied to JettyHttpConnector, JettyHttpsConnector and related configuration.

Functional tests are written to verify the configuration options are base down into the connector. Tests verify that acceptor threads are increased when accessing the application defined connector, and when accessing the connector used by the endpoint.
Added config option to set the number of acceptor threads used by Jetty. Acceptor threads are those threads dedicated to accepting incoming connections. Increasing the number of acceptor threads can increase the throughput of a running system
Broke up tests and test config so that each test defines only a single jetty connector to ensure the number of cumulative acceptor threads matches the (expected) configured value. combining multiple tests, or more specifically, multiple connectors into a single test config has the affect of producing a combined number acceptor threads across all tests.
Added test assertion method to verify the number of running acceptor threads matching the (expected) configured value.
Added some more comments in each test class on its purpose.
Changed comment in XSDs to match pattern I've seen used elsewhere.
added test of sending a request to and validating the response from jetty http/https endpoints
  - now uses static imports for asserts/matchers
  - fix import order to match Mule coding style
  - fixed line ending after braces to match Mule coding style
  - specify the method visibility on methods in abstract class
  - removed unnecessary getConfigResources in abstract class
  - removed unused XSD imports in Spring config
apply MuleSoft coding style to my getter/setter in JettyHttpConnector
Merge pull request #28 from athieme/acceptors

MULE-6988:  The jetty transport does not have an option to configure the number of acceptor threads