Closes #49

This new easy algorithm checks whether a regexp's language is an
infinite language.
Also adding an AQL test to compare with the same algorithm on finite
automata.

I want to be able to compare booleans in aql. However, when an overload
for booleans is added, aql's `print compare::PrimitiveCompare 1 2`
results in `true`, because the overload for booleans is selected.
ALT selects one of the possible overloads (unsigned ints vs bools)
which is not what we want. It should suffice to add another overload for
ints and now ALT's behaviour should be OK.

Introduce a new algorithm, regexp::properties::LanguageIsEpsilon to
check whether a language of a regexp is exactly equal to a language of
epsilon regexp.
This will be later useful in checking whether the language of a regexp
is infinite.

Similarly to previous commit, let's make this clear. We are soon going
to add a new algorithm that will check if the language is equal to
epsilon, so let's differentiate.

The name regexp::properties::RegExpEmpty is not that expressive. Let's
make clear what is going on.

and also make sure that the unique terminating symbol is unique among both
subject and pattern