Optimize getting inverse of predtable

[Broes De Cat]

Currently, requesting the inverse of a predtable is done as new InverseInternalPredTable(table)

This is especially slow if predtable itself was an inverse table, and can probably also be optimized in other cases such as bddtables (take the negation).

[Bart Bogaerts]

Improved taking inverse of a table

This fixes #254. Instead of creating inverseinternalpredtables, a smarter method now needs to be called.

→ <<cset b2d7673c22c6>>

[Bart Bogaerts]

Improved taking inverse of a table

This fixes #254. Instead of creating inverseinternalpredtables, a smarter method now needs to be called.

added a test for these changes

→ <<cset 00f06ba99c4a>>