Implement commenting for CREDITS file

The reader of CREDITS (GuiAbout.cpp) now ignores lines that start
with the number sign (#). This commit also introduces a commented
out header in CREDITS reminding any potential editor that all
changes will be overwritten by generate_contributions.py.

lib/CREDITS

@@ -1,3 +1,5 @@
+# Do not edit this file. It is created by the script generate_contributions.py
+# and any direct change to this file will be overwritten.
 @bRonen Abravanel
 @iE-mail: ronena () gmail ! com
    Support for feyn diagrams

lib/generate_contributions.py

@@ -301,6 +301,9 @@ def main(argv, contributors):
      else:
          txt_credits_data = str(as_txt_credits(contributors)).encode("utf-8")
      txt_credits = open(argv[1], "wb")
+     txt_credits.write(b"# Do not edit this file. It is created by the " \
+         b"script generate_contributions.py\n# and any direct change to " \
+         b"this file will be overwritten.\n")
      txt_credits.write(txt_credits_data)
 
      if sys.version_info[0] < 3:

src/frontends/qt/GuiAbout.cpp

@@ -61,6 +61,8 @@ static QString credits()
 			QString line;
 			do {
 				line = ts.readLine();
+				if (line.startsWith("#"))
+					continue;
 				if (line.startsWith("@b"))
 					out << "<b>" << line.mid(2) << "</b>";
 				else if (line.startsWith("@i")) {