PublicShow -- Define the projection

This module redefines variables that are included in the SWISH result set.

To be done
- Removed variables should be removed from the template as well for efficiency reasons.
Source projection(+Spec:list)
Specify the result variables. Using projection/1 at the start of a query specifies which variables are part of the result set, in what order they are displayed and, optionally, whether the results must be ordered on one or more variables or the solutions should be distinct. Each element of Spec is one of the following:
Include Var in the result. Var must appear in the remainder of the body.
As Var, respecting Annotation. Valid annotations are below. Annotations may be abbreviated, e.g. asc, desc
Order solutions in ascending order.
Order solutions is descending order
Remove duplicates wrt. this argument.
AnnA + AnnB
Multiple annotations
+ Var
Equivalent to Var:ascending
- Var
Equivalent to Var:descending

If ordering is specified for multiple variables, the result set is ordered starting with the left-most variable for which ordering is defined.