LT-15340: Update references when moving sense between entries

LT-14740: Handle references properly when deleting a sense

Ensure MSA references are updated correctly when a sense
is moved or deleted.
Inform the user when deleting a sense if that will result
in an MSA being deleted which is being used.
For now, when a sense is moved
and there is no matching allomorph in the new entry,
point to the lexeme form.
Do not display a "default sense" for an analysis
unless the analysis is a guess.

Change-Id: Icdd61f1a8713e8e18cb2b56264992201da1c2f15