add vim modeline to configure.ac
only export public symbols
add compile to .gitignore
fix bogus double escaping of metadata values
prepare for a release
Od[gp]Generator: declare meta namespace

Other generators had it already, and without this, it's not possible to
declare creation date.
text:outline-level is not style property
avoid use of boost::optional

... as libodfgen does not have hard dependency on boost yet.
set outline level in style too
Paragraph style: try to improve the implementation of outline attribute and
 to create named styles even if there appear along with a style:master-page-mage attribute...
print debug messages to stderr
configure.ac: remove -Wformat=2 and -Wformat-nonliteral to allow compilation
  with --enable-wparanoic in debug mode + add some "new" format's warnings...