Please add variable support for LR plugin

[annapuskarjova]

Load runner script generator is not able to set variable to LoadRunner script

in cukes:
And let variable "modelSectionId" equal to "4"
When the client performs GET request on api/modelsections/{(modelSectionId)}

genered script:
web_custom_request("GET to http://localhost:8080/cih/api/modelsections/**(modelSectionId)**",
"URL=http://localhost:8080/cih/api/modelsections/(modelSectionId)",

[sergeytrasko]

Mainly there are 3 use cases for it:

1. Variable is taken from response body
2. Variable is taken from response header
3. Variable is set explicitly

These 3 use cases require different handling during LR script generation

[sergeytrasko]

Already implemented, please close