Adds HTTPS support to cxserver

- Allows cxserver to run in secure mode over https protocol.
- Introduces 'cxserver' as a CLI command.
- Updated README for usage instructions.

Bug: 62201
Change-Id: I53bf0d78888f8e1d4af0600e1880aee5052977d2
Merge "Adds HTTPS support to cxserver"