Add EPL-2.0

[mlinksva]

Fixes #536

Two things needed for this to be merged:

1. 2 more 'using' examples with unmodified license files (that would be detected by licensee, thus are easy to copy examples) -- help finding those wanted, thanks!
2. SPDX to publish an official ID for the license on its website (note the approval test is failing, but that's because the test looks up OSI approval from SPDX records; that will succeed when the SPDX publishes)

[yanalunaterra]

Mind that the original EPL-2.0 text file doesn't end with a newline:

@@ -306,4 +274,4 @@
   file in a relevant directory) where a recipient would be likely to
   look for such a notice.
 
-  You may add additional accurate notices of copyright ownership.
+  You may add additional accurate notices of copyright ownership.
\ No newline at end of file

[yanalunaterra]

This question applies to all license metadata: why not reference the exact revision, i.e. https://github.com/eclipse/smarthome/blob/36c9e2717e4f89cf60a0d885e7ecc6069b338f48/LICENSE? That way, if the project ever gets relicensed (say, updated to EPL-3.0), the link won't go stale.

[wking]

… why not reference the exact revision…

+1 to that. It would be even nicer to reference a tagged release (e.g. once SmartHome cuts 0.9.0). As consumers are updated to use different licenses, I expect them to be removed from using. But still, where stable links are easy, I think we should be using them instead of floating with master.

[mlinksva]

See #555 for a different idea.

[yanalunaterra]

Also, just in case if it matches the criteria of notability (probably not), here's my JSON encoder/decoder in Erlang licensed under EPL-2.0: https://github.com/yegortimoshenko/json