normalized href in px:daisy202-load and fixed playOrder in nav-to-ncx.xsl

### px:daisy202-load
- normalize input href

### epub3-nav-utils: nav-to-ncx.xsl
- navPoints, pageTargets and navTarget that refer to the same content must have the same playOrder value
- playOrder must start at 1 and cannot skip numbers
opf: full clock values and navLabel, smil: preserve upgraded metadata

- always use full clock values in package doc
- preserve metadata when upgrading SMILs
- added default navLabel in NCX based on language attribute
- relativize landmarks to opf base
mediaoverlay-utils: lower-case metadata name comparison
Merge pull request #11 from daisy-consortium/daisy202load-and-nav2ncx-fix

normalized href in px:daisy202-load and fixed playOrder in nav-to-ncx.xsl