Call tab 'Locations' not 'Observed Locations'

Locations is shorter and clearer. Features is another suggestion by Anton, but
that is too generic for now. Right now it is just Locations. Maybe later we'll
change that.
Add function to get loop name

Loop name is muchs shorter than using nucleotide ids to indicate where a loop
is found. I've added a method to get this information for views.
Use loop name instead of nucleotide ids

We don't want to display a really long string for large loops. This way is much
shorter and for large loops.