If there is no detailed error information, it now always returns an
empty list and never null.

Now that ProB supports reals, an expression like x>y is no longer
sufficient to infer that x and y are integers.

LaTeX formulas inside tables cause various layout issues in Jupyter
Notebook, such as long sets being wrapped even when they would fit on a
single line, table columns being wider than necessary, and LaTeX
formulas being left-aligned instead of right-aligned like normal text.

In some cases, ProB apparently "unwraps" LET predicates as well,
not just existential quantifications.

Event-B/Rodin does not support LET like ProB does, so we need to use
some workarounds to provide similar functionality in Event-B mode.

This matches what almost all code already did anyway. It will also help
with fixing the problems with local variables in Event-B mode - the fix
will require conditionally parsing multiple formulas.

ProB 2 now always throws ProBError for parse errors and
ModelTranslationError is no longer used.