Add Maven POM files to build and run the SBDG Samples independently from the main project Gradle build

[jxblum]

As a Spring Boot, Apache Geode application developer, I would like the ability to run the SBDG Samples independently without having to build the entire SBDG project with Gradle.

[jxblum]

Re-opening in case the feedback we receive is positive towards this (temporary) approach for users to run the examples independent from the rest of the SBDG Gradle build.

If accepted, then we need to retrofit the following Samples:

• Boot Actuator (?)
• Boot Configuration (?)
• HttpSession Caching
• Inline Caching
• Look-Aside Caching
• Near Caching