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

What was done:
1) changed wording according to Chantel's review
Merge pull request #858 from kolinus/BACKLOG-1176-1

[DOC] BACKLOG-1176 -- Document the REST calls for Carte (Kettle Path) (P...
[PDI-12947] one connection pool created per step
[PDI-13049] - Regression: PDI 5.1 Clone Rows NULLs
Merge pull request #856 from SergeyTravin/PDI-12947

[PDI-12947] one connection pool created per step
Merge pull request #861 from akhayrutdinov/PDI-13049

[PDI-13049] - Regression: PDI 5.1 Clone Rows NULLs
Merge pull request #859 from kolinus/BACKLOG-1314

[DOC] BACKLOG-1314 - Document the REST calls for Carte (Kettle Path) Par...
BACKLOG-1314 -- Document the REST calls for Carte (Kettle Path) (Part 2)

What was done:
1) uncommented JMeter tests
2) changed comments according to Chantel notes.