course-1-1: 12-seminar-datacenter: database: first version of solution, does not work somewhy.

Here we are using two concurrent hashtables to index by two fields and a
global data pool referenced by indices. Deletion does not free up any
memory; deleted elements are not reused except in very special
circumstances (where it is easy to do).
course-1-1: 14-seminar-line-age: matrices: add solution.