Allow the environment file to be specified via URL

Environment files could be provided only as local files.

Now `--environment-file` option accepts both local files and urls.

Change-Id: I11717275fe3ca18d0849bc34d5bd30879388cb7e
Closes-Bug: #1233914
Show better error when json fail to parse template

Change-Id: I0d888fc180dd118c50b93ce4393f06d89780a0c5
Partial-Bug: 1261224
Merge "Allow the environment file to be specified via URL"
Merge "Show better error when json fail to parse template"