Fix repeated text in output

In the output text, parts of the text were repeated, because the xml
parser send xml to the act2xml method both on the beginning and end of
an act tag. This was changed to only doing it on the closing of an end
tag.
Add term vectors to event text field
Add number of words in text to index

The number of words in a text is added as a separate field in ES. This
field is used to calculate corpus statistics.