Remove hard to maintain C++ layer for accessing GenericVectors using numpy arrays.
The numpy indexing is now moved to the Python layer of GenericVector and
one have to use local indices now. Almost all functionality is kept, but one cannot
set values using python slices anymore.
Add changes to files which should have been commited last commit...
Added comment in README about changed functionality in book chapter examples
Merge branch 'johanhake/fix-issue-54-working-of-numpy-vector-interface-in-parallel'
Small fix for Python 3