Add support for assigning points to solution

[vlstill]

[vlstill]

IS MU will hopefully support points from 2020.

It should be possible to send a (pipe) file descriptor to the test script through pass_fds and let it write test log to it. This log can include points.

[vlstill]

It works with ispol & couse which is set to extended mode in exprtest config.

TODO:

• documentation & examples