Improve progress reporting in Annotation importer plug-in

[Nicklas Nordborg]

The annotation importer is a two-step process where the first step parses the file and the second step updates the database. The progress reporting is divided so that 50% is assigned to each step. This is typically good when the number of annotation is low, but the second step takes longer time as the number of annotations grows larger.

I think that we could give the second step a larger proportion. For example, for every 20 annotations. If we for example have 60 annotations the first step should take 25% and the second step 75%. We might also put a limit so that the first step never goes below 10%.

[Nicklas Nordborg]

(In [7474]) Fixes #2114: Improve progress reporting in Annotation importer plug-in