[outlineCompiler] add glyphSet arg; don't convert curves here
[outlineCompiler] add glyphSet arg; don't convert curves here

The OutlineTTFCompiler no longer takes convertCubics and
conversionError arguments, and no longer does the conversion itself.
It now expects the input glyphs to be already in quadratic format.
The conversion is now done by the preprocessor object via filters.

Outline compilers can take an optional glyphSet argument, which is
a dictionary keyed by glyph name and containing the glyphs that were
previously filtered by the preprocessor.

As these glyphs are now copies, they no longer refereces the parent
font, so we need calculate their bounding box manually instead of
relying on the controlPointBounds property (which needs the glyph's
parent font).

An left-over `self.log = []` attribute from ufo2fdk has been removed,
and its messages are now logged using regular logging module.

jamesgk/ufo2fdk,googlei18n/ufo2ft,jamesgk/ufo2ft,moyogo/ufo2ft,googlefonts/ufo2ft