change ch_name to unique_ch_name

when calling that method without re-initializing class instance.

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