Introduction of YML metadata for eclipse-cs integration

[gaurabdg]

It was decided by @romani and me, that all eclipse-cs extension projects will have eclipse-metadata.yml file which would consist metadata required during automatically generating check metadata and integrating with eclipse-cs.(PR: checkstyle/eclipse-cs#242)

For now, the required eclipse cs configuration metadata are the RuleGroupMetadata.name and related data.
Data required for third party extensions are

• extensionName - Name of the package of extension - for e.g. com.github.sevntu
• ruleGroupName - The name which would be displayed in eclipse
• ruleGroupDesc - Brief description of the extension
• ruleGroupPriority - Priority number of the rule group to determine the relative positioning in UI trees

There can be multiple group categorization.

Example yml config:

---
ruleGroups:
  - name: "SevNTU checks"
    description: "Check extensions developed by SevNTU"
    priority: 500
    package: "com.github.sevntu"
  - name: "Test package"
    description: "Test package desc"
    priority: 1600
    package: "com.github.sevntu.checkstyle.checks.test"

directory content which show cases that every package except for test falls under group "SevNTU Checks":

sevntu.checkstyle/eclipsecs-sevntu-plugin/src/com/github/sevntu/checkstyle/checks on  yml-eclipse-meta [!?] 
➜ ls -R
.:
annotation  coding  design  naming  sizes  test

./annotation:
checkstyle-metadata.properties  checkstyle-metadata.xml

./coding:
checkstyle-metadata.properties  checkstyle-metadata.xml

./design:
checkstyle-metadata.properties  checkstyle-metadata.xml

./naming:
checkstyle-metadata.properties  checkstyle-metadata.xml

./sizes:
checkstyle-metadata.properties  checkstyle-metadata.xml

./test:
checkstylemeta-NewCheck.xml

This config results in the following eclipse-cs UI tree:

[kaushal-2002]

Hi, I am a beginner at this issue can you help me? How to work on it?

[rnveach]

I am marking this issue as blocked because of issues identified at checkstyle/eclipse-cs#317 (comment) .

eclipse-cs metadata is not working with this YML in it. I don't know if it is because of the combination of XML/YML (old/new metadata) or something else.

In order to restore functionality of sevntu's eclipse plugin while investigating eclipse-cs more, the commit adding the YML should be reverted unless a fix can be found sooner.

Even if eclipse-cs' functionality is fixed, I feel this should be blocked by #864 and wait until we convert everything to the new format. This way we can be one or the other, all old or all new, and not anything in-between