Account lookup failures, account and client limits, options reload.

Changed account lookup and validation failures to be more understandable by users.
Changed limits to be -1 for unlimited to match jwt pkg.

The limits changed exposed problems with options holding real objects causing issues with reload tests under race mode.
Longer term this code should be reworked such that options only hold config data, not real structs, etc.

Signed-off-by: Derek Collison <derek@nats.io>

conf/parse.go

@@ -87,7 +87,7 @@ func ParseFile(fp string) (map[string]interface{}, error) {
 func ParseFileWithChecks(fp string) (map[string]interface{}, error) {
 	data, err := ioutil.ReadFile(fp)
 	if err != nil {
-		return nil, fmt.Errorf("error opening config file: %v", err)
+		return nil, err
 	}
 
 	p, err := parse(string(data), fp, true)