Can plugins be placed in a config.xml file? I would like to use the Google Analytics plugin. Can I just put the following code into my xml file?
<plugins>googlytics-1</plugins>
If yes, what if I want to add multiple plugins? How would the code change?
Thank you.

That should work. With multiple plugins handled like this:
<plugins>googlytics-1,embed-1</plugins>
<embed.code>Just an example of a plugin-specific config tag</embed.code>