Create U2CallHTTPandRLINK-REST

The program listed in this content shows how to use U2 BASIC's CallHTTP API to communicate with R/Link's REST API. The focus is on the /List, /FileGet, and /FilePut methods.

When the program is run, three menu options are available to the user:
1. List contents of shared folder U2upload <- this option uses the REST API's /List method
2. Display content of file in shared folder <- this option uses the REST API's /FileGet method
3. Upload file to shared folder <- this option uses the REST API's /FilePut method