Support validation parameters for service:check (#953)

* Add historic flags for the service:check command

* validationPeriod - the duration (from now) to validate the service against
* queryCountThreshold - minimum number of requests within the requested time window for a query to be considered
* queryCountThresholdPercentage - number of requests within the requested time window for a query to be considered, relative to total request count.

* Improve error reporting and fix out-of-order error throwing.

Throw errors from the response if we have them, then throw the generic
error if no data is provided. Previously, the order of these were swapped,
meaning that if a specific error came back from the server, we would still
throw the generic error.

* Update changelog

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Upcoming
 
+- `apollo`
+  - Support validation parameters for service:check [#953](https://github.com/apollographql/apollo-tooling/pull/953)
+- `apollo-language-server`
+  - Better error handling in ApolloEngineClient [#953](https://github.com/apollographql/apollo-tooling/pull/953)
+
 ## `apollo@2.4.4`, `apollo-codegen-scala@0.33.0`
 
 - `apollo@2.4.4`