Added documentation section for REST connector multipart/form-data functionality#2465

Andry925 wants to merge 5 commits intothingsboard:masterthingsboard/thingsboard.github.io:masterfrom

Andry925:docs/multipart-data-rest-connector-documentationAndry925/thingsboard.github.io:docs/multipart-data-rest-connector-documentationCopy head branch name to clipboard