[REQ] add sessionToken support to AWS4Auth

[mfriesen]

Is your feature request related to a problem? Please describe.

AWS4Auth library only supports static credentials IE: AccessKey, SecretKey credentials. Temporary credentials are better to use than static credentials because they expire after a specified interval. To support temporary credentials, the AWS4Auth library needs to support the SessionToken parameter as well.

Describe the solution you'd like

Instead of only having the AWS4Auth method:
public void setCredentials(String accessKey, String secretKey)

to add the method
public void setCredentials(String accessKey, String secretKey, String sessionToken)