FriCAS Code

add Somos option, add checkOption, clean up guessADE/guessRec/guessFE.

add colon to warnings.

beautify debugging messages, fix documentation typos.

check solutions also when guessing over prime fields, allow
polynomials over prime fields as coefficients.

prime?(): do the right thing: really ignore sign when deciding if
number is prime.

add test to see whether checking is done for guessing over prime fields, and
whether guessing polynomials with algebraic coefficients works.

Add VectorSpaceBasis domain.

Fix for 'has' test.

Ignore sign when deciding if number is prime.

Use linear solver for linear systems of expressions.