prepost.dlctemplate: using all tags uses way too much disk space, only use those necessary to uniquely define each case

revert commit 0340b1b5

sort dlc filenames when reading into list of cases to avoid random order

the random order was causing a crash in our OpenMDAO wrapper since individual nodes were reading in cases in random order.

See merge request !12

prepost.Simulations: errorlog indicates number of errors, not all line nr occurances (can be too many)

Function added to compute the total envelope of a series of envelopes

- compute_env_of_env function added: it can compute a total envelope for a series of single simulations or a general cloud of points;
- int_envelope function moved out of  Cases class;
- proj_envelope function added: it projects the envelope at given angles of a polar coordinates system and translate back to cartesian coordinate;
- compute_envelope function modified to accomadate changes genarate by moving inte_envelope out of Cases class;
- bug fixes.

See merge request !11