Refactor Maven Project Structure

- Convert client/, common/ and server/ to modules
- Add parent pom.xml
- Update templates and workflow
- Remove old documentation

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,21 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: enhancement, feature
+assignees: CyB3RC0nN0R, delvh, DieGurke
+project: Envoy
+milestones: Envoy v0.2-beta
+---
+
+**Is your feature request related to a problem? Please describe.**
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+
+**Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+
+**Describe alternatives you've considered**
+A clear and concise description of any alternative solutions or features you've considered.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.