Unary not operator in DaphneDSL

[pdamme]

DaphneDSL does not support the typical unary not operator yet; one cannot say, e.g., if(!found) ... or while(!(converged || aborted)) .... There is a workaround: if(found == false), but we should not require that, since it's quite inconvenient.

Solving this issue requires:

• changes to the DaphneDSL parser
• a new elementwise unary operator for not
• adding some script-level test cases