implement new method read_features_from_file

but not yet in use, because i do not know whether it works
Merge branch 'master' of github.com:nicolas-fricke/semmul2013-group1
add a method for reading just one json directory in general helpers
prepare combined clustering for preprocessing on the chair's server

- add two command line parameters (and delete the others except -p) -d and -r
  -d Specifies the directory which we want to preprocess
  -r Specifies whether image files should be read from disk rather than downloaded from flickr, specify image path in config file
- add image path to config template to read images from disk
- add ## to visual features filename in config template
- delete writing after 1000 lines
- if no parameter is given, the whole metadata folder will be processed

--> adapt CONFIG! add downloaded-images-dir and change visual-features-filename
delete unused import
Add bash script for automatic preprocessing