Request functionality: PTR parse SLEWs and assign display them as block

When parsing a PTR it would be useful to have SLEWs creating artificial blocks with start-, end-time, and duration (and block counter increment). The default behavior is to show them on the left-hand view (in the TOL<->PTR tab), however, the user may be allowed to apply a filter. The filter will allow to filter to show observation of only certain instruments (JANUS, UVS, MAJIS, SWI, SLEW, ALL). The PTR parsed on the right-hand does not have to be modified (or collapsed, since clicking a block automatically takes you to the proper place in that view).