v0.0.76: [Util] Add `is_allocator` concept

Without this concept, compiler would pick the templated
perfect-forwarding constructor of `doubly_linked_list`
over its copy constructor for `non const` arguments.

v0.0.75: [Backend] Update backends for minimized `Schema`.

The prior commit introduced a more rigorous minimization of `Schema`s of
`Operator`s in a plan.  This commit makes the necessary changes in the
backends to handle the new `Schema`.

So far, the `Interpreter` relied on the `Schema` not being exactly
*minimal* but simply a concatenation of the `Schema`s of both sides of a
join.  This commit fixes the implementation of the simple-hash join to
correctly use the minimized schema.  Further, we drop the requirement
that `Tuple`s be simply concatenated.

v0.0.74

[AST] Make `Expr` target references red in ASTDot.

v0.0.73: [Wasm] Improve `Decimal` class.

- Remove superfluous methods.  The once inherited from `Expr<T>` are
  already what we need.
- *Delete* (with `require false`) certain operators and methods that are
  not supported by `Decimal`, e.g. `rotl` or `neg`.

v0.0.72

[Benchmark] Fix mutable config name of experiment tpc-h/q12

v0.0.71

[Wasm] Implement Decimal type.

v0.0.70

[Benchmark] Fix TPC-H Q3 for HyPer.

v0.0.69

[Benchmark] Add TPC-H benchmark chart config.

v0.0.68: [Benchmark] Revert change of operators benchmark

Reducing the number of tuples was never intended to be committed.

v0.0.67: [CMake] Link the `check` binary with complete lib

We must link the `check` binary with our complete library, s.t. at least
one `DataLayoutFactory` exists.  That is, because processing `CREATE
TABLE` statements requires creating and assigning a `DataLayout` to the
`Table` instance.