0.90.2-beta1 Rocket power!

Changes:

• Extensive optimization of decoding (serialization), parsing
  (KtXmlReader) including the creation of the xmlDescriptors.
• Add a new preset fast for a config/policy that chooses speed over
  verification (such as element order). It still requires "correct"
  xml files.
• Add "work in progress" xml schema module to the dev branch. This
  is not yet ready for release (but will parse most xml schemas)
• Have the XmlReader.{version,standalone,encoding} properties be
  retained by all readers (as existing parsers behave); reading these
  values before the document declaration was seen (or known to not be
  present) is non-deterministic.
• Make the value of the depth property of XmlReader consistent
  for EndElement values. The depth of an endEvent uses the android
  XmlPullParser semantics
• In the case of a polymorphic value child (or list of polymorphic
  children as value child), when an unknown tag is encountered, allow
  this to be matched against a single! XmlSerializer from the module.
  This aids #225.

Fixes:

• Fix NodeSerializer in the serialization module to properly forward
  to the actual implementation.
• Don't make the companion of XmlDeclMode internal (#219). This is a
  workaround for a regresion in 2.0 that doesn't allow resolving enum
  constants in this case.
• Fix deserialization with contextual serializer #220
• Fix NamespaceHolder.namespacesAtCurrentDepth for nested
  declarations.