Ticket default_description cannot include new lines

[Ryan J Ollos]

Two issues were discussed on the ​mailing list:

1. It should be documented that lines 2:end need to be indented with whitespace to have a multi-line ticket description. For example,

   [ticket]
   default_description = line1 
    line2
    line3
    line4
   

   This would be applicable to any textarea. Description is currently the only one in [ticket] section (TracIni#ticket-section), but we may also need to consider the value parameter of textarea custom fields (TracTicketsCustomFields#AvailableFieldTypesandOptions).

2. Empty lines can't be included in the [ticket] default_description because ConfigParser in Python 2.x does not appear to support empty lines. The empty lines are stripped out. We'll need a workaround such as specifying empty lines with a single \ character, and then stripping out the character before rendering an empty line in the ticket description.