uart: Put annotations into proper annotation types.

There are now extra annotation types for data, start/stop/parity bits and
for warnings (e.g. "invalid parity" or "frame error" or such).

This allows users to select which of the annotation types they want to
see (they can select one/multiple/all annotations as needed), and also
allows them to use different visual representation for the different
annotation types in GUIs (e.g. different colors for the blobs, different
fonts, rectangle/round/elliptic blobs, and so on; how the annotation
blobs are displayed is entirely up to the GUI and its configuration by
the user).