Start extensive refactoring on lambda.go

 * add tests for fetch function
 * extract methods to prepare and send requests
 * move timestamping closer to request execution
 * create a struct holding the state of lambda execution
 * simplify method calls
 * break down runLoadTest method to simplify cascading for loops
 * simplify spawn logic for request worker go routines
 * extract lambdaSettings as struct
 * move code for the lambdas initial state into setup methods
 * setup some default values for lambda
 * create various tests for runLoadTest
 * extract method to parse lambda settings
 * simplify requestParameters
 * extract calculation of intermediary results to separate structs
 * introduce request metric struct to reduce complexity of result calculaton
 * add timeout tests
 * introduce interface for SQSAdapter to mock during testing
 * use elapsed to calculade lastRequestTime for more precise results
 * add tests for quitting on lambda timeout
 * assert last result is sent on timeout
 * apply rename refactoring to functions and variables
 * allow to fork into new AWS Lambda on AWS timeout

Author: cwaltken-edrans