Reduce context menu in investment plan transaction list

The full menu includes buy, sell, inbound and outbound delivery which
is confusing to the user as he will never see those transactions in this
view.
Investment plan log updated
Separate menus for benchmark and performance data series

Issue: #85
Make quote import from finanzen.net more robust

Make the parsing stop after the content table is finished, so that
tables comming afterwards do not make it fail.