- Unified the HTTP client connector parameters (socket connection to 15s,
        idle socket to 60s, socket stop to 60s, max connections per host to 10,
        max total connections to 20). Suggested by Kristoffer Gronowski.
 - Fixed stop idle time.
Improve null handling when adding custom header
 - refactored Firewall design to properly separate service from filter and move FirewallFilter in private packages
 - refactored Introspector class to hide private classes from public API
 - removed warnings in APISpark extension
 - refactored Firewall design to properly separate service from filter and move FirewallFilter in private packages
 - refactored Introspector class to hide private classes from public API
 - removed warnings in APISpark extension
Merge branch 'master' into apispark-2.3

Conflicts:
	modules/org.restlet.ext.apispark/src/org/restlet/ext/apispark/Introspector.java
	modules/org.restlet.ext.apispark/src/org/restlet/ext/apispark/JaxRsIntrospector.java
	modules/org.restlet.ext.apispark/src/org/restlet/ext/apispark/internal/firewall/FirewallFilter.java
	modules/org.restlet.ext.apispark/src/org/restlet/ext/apispark/internal/utils/IntrospectionUtils.java
 - Fixed Eclipse warnings
 - Jackson representation now ignore empty value (null or empty collections)
   by default in the JSON/XML/CSV/YAML produced, leading to more compact
   representations.
 - Added unit test for exceptions serialization with Jackson.
 - Improved Jackson exception test case
Merge pull request #972 from boillodmanuel/issue971-improve-null-handling

Improve null handling when adding custom header
 - deprecated static HttpRequest.addHeader method in engine to favor usage of new Message#getHeaders() method
move method HttpClientHelper.getSocketConnectTimeoutMs() to parent class
fix edition GWT
fix GWT edition: add StringWriter.close() in gwt version
Merge branch 'master' into apispark-2.3
issue #216 - Remove HeaderName. Use simple String instead.
typo and suggestion from @addenie
issue #216 - Follow CORS steps
Update CORS api
fix GWT Edition