[DOC] BACKLOG-1176 -- Document the REST calls for Carte (Kettle Path) (Part 1)

What was done:
1) added javadoc to 13 servlets
2) added JMeter tests
Merge pull request #842 from kolinus/BACKLOG-1176-1

[DOC] BACKLOG-1176 -- Document the REST calls for Carte (Kettle Path) (P...