Create a common EC2 connection argument spec for EC2 modules

##### Issue Type:

Feature Pull Request

##### Ansible Version:

Based on:
ansible 1.5 (devel a0f91f2aaa) last updated 2014/02/05 20:43:12 (GMT +1000)

##### Environment:

N/A

##### Summary:

Refactor the currently well-factored ec2 modules (i.e. those that already use ec2_connect) to 
have a common argument spec. The idea is that new modules can use this spec without duplication
of code, and that new functionality can be added to the ec2 connection code (e.g. security 
token argument)

##### Steps To Reproduce:

N/A

##### Expected Results:

No actual change in functionality

##### Actual Results:

No apparent actual change in functionality of the modules I've tested