* check_bbbike_temp_blockings: make sure the id counter works also for
  undefined entries

  This is needed for the next change in bbbike-temp-blockings.pl.
* undef'd two old entries in bbbike-temp-blockings.pl

  These entries had neither a file nor a data entry, and thus caused
  warnings in the error.log while running cgi-mechanize.t. Now these
  two entries are set completely to undef, the old contents are
  available in comments.
* BBBikeTest: new functions libxml_parse_html and
  libxml_parse_html_or_skip
* cgi-test.t: prototypical use of new libxml_parse_html_or_skip function
* cgi: don't reuse the BBBikeGrafik window anymore

  In modern browsers the former behavior was confusing, as on 2nd time
  an existing tab was reused, but did not get the focus and was not
  raised. The user could only notice something by watching at the tab
  title which shortly says "Connecting".

  For old non-tabbed browsers this means that multiple windows with
  the graphics may be opened, but this is acceptable.

  So now the target is simply "_blank", and every time a new
  tab/window is created.
* cgi: removed "Reset" button

  Code is only commented out; maybe I will re-use it for a setting
  selector.
* bbd2mapservhtml.pl: unset imagetype parameter if showroutelist is set

  This is to prevent confusion later in the cgi --- no harm happens
  currently, but this just depends on the CGI param evaluation order.
* BBBikeMapserver: create route_shape_file only once

  Previously, in every scope iteration the same shape file was
  created.
* mkroutemap: removed unused FindBin
* created new function get_visible_map_bbox_polar

  Code was in BBBikeFlickrPlugin, now it's available for all in
  bbbike.
* added quick'n'dirty OpenWeatherMap plugin
* check_bbbike_temp_blockings: better diagnostics if temp blocking
  file is invalid (i.e. show $@)
* data update (MyFest)