Prepare work for easier updating of upstream g'mic

• work on regression tests
  • now we parse correctly all the filters from 1.6.1.0 release
• improve parser:
  • support also @gimp_en tags to include all english filter definitions,
  • fix generation of gmic commands which include singe command name without parameters
  • regenerate regression test file gmic_def_1610_krita.xml
• do not install gmic_def.gmic anymore, use updateXXXX.gmic instead
  • new gmic releases ship gmic.h which is produced from updateXXXX.gmic
• tests need to identify filter by full path (category/subcategory/filter-name)

• drop filterCommands.txt which consisted of manually picked gmic commands, replaced by automatic dump of filters (gmic_def_1610_gimp.xml) produced by hack in gmic for gimp plug-in: now krita's gmic parser can be compared to 623 g'mic filter definitions