Add CHANGELOG

CHANGELOG

+Version 6.0
+===========
+    * Grass7 compatibility
+    * Parallelized process in step2, step3 and step4
+    * ZirkelKill ported to Python3, no more Java dependency
+    * Launch scripts now accept an optional parameter to specify where to find the config file (with any name)
+    * Advanced progression display
+    * Automatic grass environment building, no more need to build a "case"
+    * Flexibility in config file values path (accepts relative and absolute path)
+    * Flexibility in user location when running launch scripts
+    * New launch script to run all steps
+    * No more system calls (to awk, grep, sed...) -> code is now full Python3 and portable to Windows
+    * Use pipes between grass tools to avoid some hard disk access (avoid writing some intermediate files)
+    * Added GNU license and list of author(s)
+    * Added simple tests for config file parameters
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