Create subReaders lazily

Should improve memory usage
Use True/False instead of 1/0
Move fontTools.ttLib.importXML to fontTools.misc.xmlReader

Better matches xmlWriter.
Add font.lazy
Default to non-lazy for ttx
Port ttLib to respect font.lazy

I *hope* I didn't break anything...

Notably, cffLib is not ported yet.
Remove unused method
Remove unused fontTools.misc.psLib
Remove unused fontTools.misc.psOperators
Remove unused and unmaintained fontTools.ttLib.test.ttBrowser
Remove "optimization" re Extension lookups

Historically, Extension lookups were only decompiled upon access,
and decompiled Extension lookups were possibly copied verbatim to
output when compiling.  This discrepancy with all other table types
is confusing and undeed.  The possible time saving is not worth the
loss in possible optimization of table data.  Remove.