issue2551099 - disable processing of data url's in markdown. Display as plain text. Added 'data' to templating.py _disable_url_schemes array. User should be able to re-enable it by changing the array from the tracker's interfaces.py. Markdown tests failed before the change to _disable_url_schemes. Also add second separate data test for ReST and plain text processing. data url's look like they are already ignored in these proess streams.

--- a/roundup/cgi/templating.py	Sat Oct 31 14:54:46 2020 -0400
+++ b/roundup/cgi/templating.py	Sat Oct 31 15:43:53 2020 -0400
@@ -20,7 +20,7 @@
 __docformat__ = 'restructuredtext'
 
 # List of schemes that are not rendered as links in rst and markdown.
-_disable_url_schemes = [ 'javascript' ]
+_disable_url_schemes = [ 'javascript', 'data' ]
 
 import base64, cgi, re, os.path, mimetypes, csv, string
 import calendar