Created a Spring Data GemFire Starter POM

... as well as a Spring Boot Sample Application with associated tests
for demonstrating how to get started using both Spring Data GemFire
and GemFire.
Fix versions and repository declarations

Fixes gh-606
remove obsolete EmbeddedServletContainer.NONE
Fix ordering in starters pom
Polish dependencies pom

 - Consistent use of tabs
 - Consistent ordering
Align couchbase more with other data-* support
Revert JDK8 travis change (seem to be failing)
Backout couchbase changes
Use Jedis rather than Lettuce as preferred Redis client

Salvatore has indicated that Jedis is his Java Redis client of choice.
This commit updates the auto-configuration support, actuator and
Redis starter accordingly.

Completes #745
Upgrade to Groovy 2.3.0-rc-2
Remove remnants of Couchbase starter
Add generic error handling to BasicErrorController

Since Spring supports gobal error handling through
@ControllerAdvice, it is quite easy to set up more meta-data
about an exception for the BasicErrorController. You need
to be careful not to swallow Security exceptions, and probably
others (optionally) so this feature needs a bit more work.

See gh-538
Move ErrorController to autoconfig
@WebApplication->@WebAppConfiguration

Fixed gh-746
Add FreeMarker support

This commit adds auto-configuration and a starter,
spring-boot-starter-freemarker, for using FreeMarker view templates in
a web application.

A new abstraction, TemplateAvailabilityProvider, has been introduced.
This decouples ErrorMvcAutoConfiguration from the various view
technologies that Spring Boot now supports, allowing it to determine
when a custom error template is provided without knowing the details of
each view technology.

Closes #679
Polish spring-boot-starter-data-gemfire's pom
Replace column name using reserved keyword

This commit replaces the "index" property of Review to use a custom
column name ("idx") as index is a reserved keyword in some RDMS such
as Oracle and MySQL.

Fixes gh-752
Upgrade to Reactor 1.1

Fixes gh-706
Add support for HikariDataSource

We still prefer Tomcat if it is available (that can change
if the community asks loudly enough). Hikari is supported
via the same spring.datasource.* properties as Tomcat (and
DBCP), with some modifications:

* The validation and timeout settings are not as fine-grained
in Hikari, so many of them will simply be ignored. The most
common options (url, username, password, driverClassName) all
work as expected.

* The Hikari team recommends using a vendor-specific DataSource
via spring.datasource.dataSourceClassName and supplying it with
Properties (spring.datasource.hikari.*).

Hikari prefers the JDBC4 isValid() API (encapsulates vendor-
specific queries) which is probably a good thing, but we
haven't provided any explicit support or testing for that yet.

Fixes gh-418
Convert actuator-ui sample to FreeMarker

See gh-679