Add ability to resume from different step in lambda-install-aws.sh

[dimkir]

This may happen that in case you have not assumed correct AWS permissions that lambda funciton installation may fail somewhere in the middle. Ability to resume from 2nd or 3rd step is extermely useful:

In the example below, I managed to go through the first step (role creation) but choked on the seocnd one - Policy creation. Now my only option is to change name of the function and start over. Would be great to have ability ./lambda-install-aws.sh --resume-from create-policy