INT-1639: Add <spel-function> support

* add `<spel-function>` XSD element
* add `SpelFunctionParser`
* add `SpelFunctionRegistrar` to avoid introducing some confused 'Method'-bean
* add `SpelFunctionRegistrar` collaboration with `IntegrationEvaluationContextFactoryBean`
* some refactoring for `IntegrationEvaluationContextFactoryBean`
* polishing some failed tests after this change

JIRA: https://jira.springsource.org/browse/INT-1639

INT-1639: SpelFunctionParser use BeanClassLoader

INT-1639: Inherit 'functions' from parent AC

INT-1639: Document the <spel-function>

INT-1639: 'NoSuchBeanDefinitionException' fix

Polishing
INT-3122 Return String Properties as String

Make converted object toString() behave as expected
INT-3132 Add minSubscribers to Pub/SubChannel

Send is deemed to be successful if sent to at least this
number of subscribers (default 0).

Note: when using a task executor, if there is at least one
subscriber, a send is always good, regardless of success
or failure of invoking the handler.

Polishing - Docs - PR Comments
[artifactory-release] Release version 3.0.0.M3
Revert Version to 3.0.0.BUILD-SNAPSHOT
Add Artem to POM Developer List
Contributing wiki: JIRA links note
INT-3075: Note regarding HTTP Status Code

JIRA: https://jira.springsource.org/browse/INT-3075
INT-3138: add `awaitTermination` to delayer tests

`DelayerHandlerRescheduleIntegrationTests` fail sometimes
on asserts. Looks like `context.destroy()` works very slow
and `<delayer>` manages to send delayed Messages

JIRA: https://jira.springsource.org/browse/INT-3138
INT-3092, INT-3042: Doc: Jacksons, Resequencer

JIRA: https://jira.springsource.org/browse/INT-3042
https://jira.springsource.org/browse/INT-3092
INT-3120: Remove `Accept-Charset` from Response

`StringHttpMessageConverter` adds `Accept-Charset` header by default.
By RFC 2616 `Accept-Charset` is a Request header,
so it won't be presented in the response.

Turn off `writeAcceptCharset` in the `HttpRequestHandlingEndpointSupport`.

JIRA: https://jira.springsource.org/browse/INT-3120
INT-2117: Test that trim() Works in the AMMR

* `AbstractMappingMessageRouter#addChannelFromString` uses
`StringUtils.tokenizeToStringArray`, so it's enough to check it from test.

JIRA: https://jira.springsource.org/browse/INT-2117
INT-3117: Add r-c & r-t Attrs. to Chain Gateways

* Add `reply-channel` and `reply-timeout` to `<gateway>` within `<chain>`
* Add appropriate asserts to `ChainParserTests`

JIRA: https://jira.springsource.org/browse/INT-3117
INT-3024: Add <poller> to mongodb:o-c-adapter

In addition add `<request-handler-advice-chain>`

JIRA: https://jira.springsource.org/browse/INT-3024
INT-2739: StoredProc: 'row-mapper' as a Bean Ref

* Convert `row-mapper` attribute of stored procedure components
to bean reference
* Class name is also supported for backward compatibility

JIRA: https://jira.springsource.org/browse/INT-2739
INT-3098 TCP Suppress Error Log on Normal Close

Net connections suppress error logs, NIO connections did not.
INT-3029 JPA: Support Iterables for Persist/Merge

* Add test cases
* Add documentation

Jira: https://jira.springsource.org/browse/INT-3029

INT-3029 Update copyright year

Doc Polishing
INT-3129: FTP local-filename-generator-expression

* Add `local-filename-generator-expression` attribute to FTP and SFTP Outbound Gateway
* Refactoring for `(S)FtpOutboundGatewayParser`
* Add `local-filename-generator-expression` tests
* Add 'What's New' and attribute description

JIRA: https://jira.springsource.org/browse/INT-3129

Polishing

Doc Polishing

Assert attribute is only set for get/mget

Move tests to the get gateways
INT-2433: Get Rid of MessageProcessors wrapping

Previously, provided `MessageProcessor` to create a `MessageHandler`
for endpoint was wrapped to `MethodInvokingMessageProcessor`,
e.g. `GroovyScriptExecutingMessageProcessor`.

Check the type of provided object in the constructor
of `MethodInvoking*` strategies and use it directly if it is `MessageProcessor`

JIRA: https://jira.springsource.org/browse/INT-2433
INT-3139: Add #jsonPath SpEL Function Support

* #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