Documentation refinements; store Unicode characters as is

Enabled docbook file installation
Handbook corrected, notice about no content added
Revised README file
installer: try using su when sudo is not available

Non-ASCII characters are now stored in plain text, not in HTML entities
(Conversion was introduced in kelvie/basket@125be15 and
it broke search in non-ASCII notes)
Utf-8 mark in HTML; doc/CMakeLists.txt fix

Insert  <meta ... charset=utf-8> into note HTML source
Always use utf8 in BasketScene saving/loading
Included doc/en subdir to cmake
Fix tags fonts and colors; display notes tooltips

Handle tag- and user-defined fonts and colors via
self-made QTextDocument-to-HTML convertion (textDocumentToMinimalHTML)
Added onFontSelectionChanged slot to handle FontComboBox changes
Properly handle tooltip event for notes and basket scene
merged UTF-8 HTML, tags fonts and colors, documentation