Right indexing of frame columns by bit vector

DaphneDSL supports various ways of right indexing rows/columns of matrices/frames, i.e., to extract certain rows/columns of a data object (see DaphneDSL language reference in the documentation). One option is to use a bit vector as the indexes, where each bit indicates whether to extract the corresponding row/column.

However, this is not supported for indexing columns of frames yet. In particular, we need:
- appropriate inference of type and frame labels for `FilterColOp`, in case the input is a `Frame`
- a specialization of the `filterCol`-kernel for `Frame`
- corresponding unit test cases (in `test/runtime/local/kernels/FilterColTest.cpp`) and script-level test cases (in `test/api/cli/indexing/`)
- update of the DaphneDSL language reference in the documentation

Search for `#484` in the code base.

Search the code base for #484, then inspect FilterColOp and the filterCol kernel for the existing matrix behavior. Add the requested unit cases in test/runtime/local/kernels/FilterColTest.cpp and script-level cases under test/api/cli/indexing/. Done means frame column indexing by bit vector has correct type and labels, tests pass, and the DaphneDSL language reference is updated.

Written by the indexing model from the issue text.