Shorten common script parameter name

It's neither Python-specific, nor exclusive to the `imcflibs` package,
so the former name was quite misleading.

Author: ehrenfeu

tests/imagej/bioformats/import_image/test_01.py

@@ -1,11 +1,11 @@
-# @ File (label="Select the python-imcflibs testdata directory", style="directory") PYTHON_IMCFLIBS_TESTDATA
+# @ File (label="Select the IMCF testdata directory", style="directory") IMCF_TESTDATA
 
 import os
 from imcflibs.pathtools import join2
 from imcflibs.imagej import bioformats
 
 
-testfile = join2(PYTHON_IMCFLIBS_TESTDATA, "systems/lsm700/beads/10x_phmax.czi")
+testfile = join2(IMCF_TESTDATA, "systems/lsm700/beads/10x_phmax.czi")
 print(testfile)
 
 assert os.path.exists(testfile)

tests/imagej/bioformats/write_bf_memoryfile/test_01.py

@@ -1,12 +1,11 @@
-# @ File (label="Select the python-imcf-libs testdata directory", style="directory") PYTHON_IMCFLIBS_TESTDATA
-
+# @ File (label="Select the IMCF testdata directory", style="directory") IMCF_TESTDATA
 
 import os
 from imcflibs.pathtools import parse_path
 from imcflibs.imagej import bioformats
 
 
-components = parse_path("systems/lsm700/beads/10x_phmax.czi", PYTHON_IMCFLIBS_TESTDATA)
+components = parse_path("systems/lsm700/beads/10x_phmax.czi", IMCF_TESTDATA)
 full_path = components["full"]
 bfmemofile = components["path"] + "." + components["fname"] + ".bfmemo"