Implement bullet list generation.

* bzrlib/tests/doc_generate/builders/test_texinfo.py:
(TestListGeneration): Start testing list generation with bullet list.

* bzrlib/doc_generate/writers/texinfo.py:
(TexinfoTranslator.depart_paragraph): Paragraphs should be
followed by a blank line.
(TexinfoTranslator.depart_compact_paragraph): No difference
between paragraphs and compact paragraphs so far.
(TexinfoTranslator.visit_bullet_list)
(TexinfoTranslator.depart_bullet_list): Implement bullet list.
(TexinfoTranslator.visit_list_item)
(TexinfoTranslator.depart_list_item): Implement list item.