Use different delimiter for `OTEAPI_PLUGIN_PACKAGES`

[CasperWA]

The current delimiter, a colon (:), disallows the usage of URLs in the OTEAPI_PLUGIN_PACKAGES value, as it will incorrectly split these values up after the "scheme" has been given.

What should the delimiter be? A double colon (::)?

[CasperWA]

Suggestion from @jesper-friis is to use a unix pipe character instead (|).