move cfg to loggers + refactor + log fn wrappers

1. Instead of maintaining a global config, each specialized logger
now stores its config.
2. Refactored logInterface to elektronLogger.
3. Refactored loggerImpl to baseElektronLogger to be consistent with
the rest of the code base.
4. Wrapped elektronLogger#Log(...) and elektronLogf(...) so that we
do not have to use the instance of elektronLogger everytime we want
to log. Instead, we just do logging.Log(...) or logging.Logf(...).
5. Wrapped elektronLogger#WithFields(...) and
elektronLogger#WithField(...).
6. Refactored codebase to adhere to the changes.

logging/loggerConfig.go

@@ -1,6 +1,7 @@
 package logging
 
 import (
+	"github.com/pkg/errors"
 	log "github.com/sirupsen/logrus"
 	"gopkg.in/yaml.v2"
 	"io/ioutil"
@@ -47,16 +48,18 @@ type LoggerConfig struct {
 	Format []string `yaml:"format"`
 }
 
-func (c *LoggerConfig) GetConfig(logConfigFilename string) *LoggerConfig {
+func GetConfig(logConfigFilename string) (*LoggerConfig, error) {
 
 	yamlFile, err := ioutil.ReadFile(logConfigFilename)
 	if err != nil {
-		log.Printf("Error in reading yaml file   #%v ", err)
+		return nil, errors.Wrap(err, "failed to read log config file")
 	}
+
+	c := &LoggerConfig{}
 	err = yaml.Unmarshal(yamlFile, c)
 	if err != nil {
 		log.Fatalf("Error in unmarshalling yaml: %v", err)
 	}
 
-	return c
+	return c, nil
 }