This change allows us to calculate program paths from all programs (as
long as they don't contain any try-catch). Using this, we should be able
to calculate ALL wlps for the programs. However, the checks are not
complete for the whole program, as only program paths up to a certain
length are checked. Any further program paths might say that the program
is (in)correct and give a different result.

The WLP of a subset of statements in the language can now be calculated.
This needs to be extended, but it gives a basic idea of what we can do.

I made new types for the logical expressions (and the mathematical
expression in them) rather than reusing the datatype within the
language. I feel that there's a benefit to separating these, showing
when we're talking about the programs and when we're talking about the
wlp and its calculation and the like. However, this does increase the
amount of types we use. I think the benefit outweighs the cost of having
extra types, but I also feel like we should discuss this :)

Extended the GCL Parser/Lexer to also parse/lex RepBy

See merge request !1

In case anyone wants to use a sandbox, this should make sure that is not
being pushed. Also makes sure the build is not pushed.

Comes with a .cabal file that says to use z3, but you gotta install it
first. This is *kind of* involved and so we should just do that
together.