Convert Textile markup to Markdown

This ticket is mostly here as an example of formatting we may want to preserve.

links

• Git
  • 427b6fd1948cb3257009fc2d240ef9ccc23958bf
  • debian/changelog
• issues
  • #15878
  • #15878-note_2
• external
  • link with specific text

text formatting

code

inline code

lines
of
code

misc

• bold
• italic
• Deleted

lists

• first level
  • second level
  • bla
    • third level
    • bla

1. numbered, 1st level
   1. 2nd level
   2. 2nd level
2. numbered, 1st level
   1. second level

.h1

Quoting someone

Parent Task: #15878

Original created by @intrigeri on 17241 (Redmine)