This is a fairly major refactoring of coerceValue which returns an Either so it can return a complete collection of errors. This allows originalError to be preserved for scalar coercion errors and ensures *all* errors are represented in the response.
This had a minor change to the logic in execute / subscribe to allow for buildExecutionContext to abrupt complete with multiple errors.
ref: graphql/graphql-js#1133
Lifted from / inspired by a similar change in graphql/graphql-js#722, this creates a new function `printError()` (and uses it as the implementation for `GraphQLError#toString()`) which prints location information in the context of an error.
This is moved from the syntax error where it used to be hard-coded, so it may now be used to format validation errors, value coercion errors, or any other error which may be associated with a location.
ref: graphql/graphql-js
BREAKING CHANGE: The SyntaxError message does not contain the codeframe anymore and only the message, (string) $error will print the codeframe.
