changed z85 header and comment syntax and parser

TODO

@@ -17,6 +17,30 @@ vault checksum: add keysigs as well
 
 enable formats for secret key exports as well
 
+Z85 headers:
+ - currently I use "----- BEGIN ... -----" and "----- END ... -----" as
+   header and footer for various z85 encoded outputs. The problem is, that
+   the "-" character is part of Z85 chars. An input of 0xc6,0x5a,0x0b,0x13 would
+   result z85 encoded as: "-----". So, I cannot be sure, when I find a header
+   delimiter, if it's really a delimiter or legitimate z85 encoded content.
+   Therefore, another delimiter must be used. "~~~~~ BEGIN .... ~~~~~" seems
+   to fit best and "~" is unused in Z85. 
+   Then the parser can be enhanced as well. Eg: on startup if a ~ occurs,
+   ignore input until the first non-~ appears. Then decode input until a
+   ~ or eof appears, ignore everything after. Comments would still be a
+   problem though. Currently I ignore lines containing whitespaces. But
+   if a file is read blockwise and the blocksize is very small, then a
+   comment line may span multiple blocks and isn't recognizable as a
+   "line" anymore. Maybe, comments shall start and end with a ~ as well, eg:
+   ~ BEGIN KEY ~
+   ~ Hash: 987298347 ~
+   [z85]
+   ~ END KEY ~
+   Here I use the same aproach for the headers, since there would also be
+   the problem how to recognize them properly if a header crosses boundaries
+   or something. By using this scheme, if a ~ is found everything following
+   is marked as to be ignored which could be saved as a state when using
+   blockmode.
 
 PCPSTREAM changes:
  - enable determine armor mode of input, parse headers, comments