Message position and duration is not configurable

Problem/Motivation

The toast.js library has several options available for positioning the system messages but the module does not provide any configuration options to change them. The duration configuration option is currently only general, but the warning and error messages are hard-coded to 10s.
Warning and error messages have the same colour.

Proposed resolution

To have these more configurable, we can provide extra options in the existing admin config form and update the javascript.
Change the error message colour to red.

User interface changes

Provide the position selector for all messages and the duration selector for all 4 types of system messages.