How do you sheathe your sword? Also, how do I change the default controls?

How do you sheathe your sword in The Witcher 2? Guards are attacking me in Flotsam and I have no idea how to do it.

Less specifically, is there anywhere I can look at (and ideally change) the default controls?

The launcher contains the video and in game options, it's a bit hidden (screens are from GoG version):

Start the launcher, click on Video and Language

In the options which are mainly video settings, there is a button below names Input Settings..., click that.

Double click on current key value for an action, it will turn red, then enter your desired key for that action. Some keys are not bindable to anything else, like I for Inventory or J for journal. That put me off, too, since I use the ZGHJ layout and everything else around it.
You can also find gamepad settings here (Tab Gamepad)

You can draw and sheathe your steel sword with 1, and your silver sword with 2.

For changing the key mappings see Bora's excellent answer.