Add Maven/Gradle wrappers

[chyt]

We should include Maven and Gradle wrappers (when we begin to add Gradle instructions) to the guide repositories so that the user can run the projects without having Maven and/or Gradle pre-installed.

[gkwan-ibm]

• for guides-common, update the guide_prereqs.json to remove the Maven pre-req
• for each guide
  • update the instruction in README for the different platforms (See the spring-boot guide)
  • handle the sub-folders (multi projects)
  • update test scripts
  • make sure the cloud hosted guide conversion

each guide at least requires 0.5 PD