src: new module markdown.nit to convert ADoc to HTML

Signed-off-by: Jean Privat <jean@pryen.org>
ni_nitdoc: use the module markdown

Signed-off-by: Jean Privat <jean@pryen.org>
ni_nitdoc: display doc in <div>, not in <pre>

Signed-off-by: Jean Privat <jean@pryen.org>
ni_nitdoc: add css for nitdoc elements

Signed-off-by: Jean Privat <jean@pryen.org>
libthml: add HTMLTag::add_raw_html

Signed-off-by: Jean Privat <jean@pryen.org>
src: add new program test_markdown.nit

Signed-off-by: Jean Privat <jean@pryen.org>
tests: sav/test_markdown.res

Signed-off-by: Jean Privat <jean@pryen.org>
lib: remove duplicated documentation in string

Signed-off-by: Jean Privat <jean@pryen.org>
lib: improve examples in documentation

Instead of

    #     bla # -> res

Use

    #     assert bla   == res

Signed-off-by: Jean Privat <jean@pryen.org>
array: fix Array::swap_at

Signed-off-by: Jean Privat <jean@pryen.org>
src: fix example for String::unescape_nit

Signed-off-by: Jean Privat <jean@pryen.org>
Merge branch 'markdown'