[#505] Expressions evaluation and improved conditionals

Description

It is actually quite easy to provide convenient expressions evaluation in Lorentz because stack machine is inherently adapted for this. We only need to add some binary operators for that.

Now it is possible to write:

if dup |>| push @Natural 1 |&|
   dup |*| push @Natural 2 |<| push @Natural 10 
then ...
else ...

Related issue(s)

Resolves #505 (closed)

Resolves #506 (closed)

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