* #jsonPath function is registered automatically if the library is on the classpath
* Add otional dependency on `com.jayway.jsonpath:json-path` artifact
* Add `JsonPathUtils` class as a wrapper around `JsonPath`
* Add `#jsonPath` tests for: `<transformer>`, `<filter>`, `<splitter>`, `<router>`
JIRA: https://jira.springsource.org/browse/INT-3139
INT-3139: Further improvements
* Remove `SpelFunctionRegistrar`
* Introduce `SpelFunctionFactoryBean`
INT-3139: Polishing
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