xpath with namespaces:

- xpath can not handle explicit namespaces, only abbreviations
  accompanied with namespace mapping dictionary
- allowing "{namespace}tagname" in xpath expressions by
  - replacing explicit namespaces with (generic) abbreviations
  - constructing a mapping accordingly
map default namespace of root node for xpath
fix a problem in comparing plain/unicode strings
Merge remote-tracking branch 'upstream/master' into quakeml

Conflicts:
	seishub/core/util/xmlwrapper.py
Merge remote-tracking branch 'upstream/master' into quakeml
Merge branch 'master' into quakeml
Merge branch 'master' into quakeml
Merge branch 'master' into quakeml
make it possible to use xml files with style sheets when default namespaces are involved
fix prepending default namespace in xpath in case of `[...]` selections
with predicates
minor fix
Merge pull request #10 from megies/quakeml

namespace workaround for compatibility with seishub.plugins.seismology after quakeml switch