Merge branch 'next'

* next:
  minor, provide --explode-by-interval in ute-slab
  minor, descend into aux/R/ if R DSO building is requested
  chore, check for R installation (and its flags)
  chore, move matlab auxiliaries to matlab/ subdir in aux/
  test, write simple mini plot files as SYM_mini.png
  Revert "test, check how to draw the line chart into the hmap"
  test, check how to draw the line chart into the hmap