Http syntax Improvements

[cedric05]

1. Json keyword is no longer required, its optional
2. Empty http file is valid http file
3. Import suggestions shows classes//names from imported file

Any new Feature should handle all of below

• http2har (export to all programming languages using httpsnippet or request sharing)
• har2http (swagger3 import, swagger2 import, curl import)
• postman2http (postman3 postman2 import)
• http2postman (export http file to postman request collection)
• http2curl (mirror, to check syntax or most scenarios)

are expected to work by default for any new feature. here is the checklist

• check request executed properly
  • test case
• check har is generated properly and test case
  • test case
• check postman collection export of that use is generated properly
  • test case
• check with this new feature, postman import (few left out) can be bought back
  • test case
• check curl is generated like expected
  • test case
• check format is generated as expected
  • test case