cleaned up conf files:
- removed comments and empty lines
- removed key-value pairs with no value and several unused keys
- removed classifiers and evaluation metrics that are disabled (to reduce bloat of conf files). Removed values that are the same as the default value set in confrc to reduce bloat futher.
- replaced tokenizer->keep_only_IT with feature_selection->ensure_vectors_exist and enabled feature selection where needed
- Several other minor changes relating to the removal of unneeded options from conf file (e.g. various bits of code expecting something to be there when they have a default value for handling the case when it is missing)
Merge remote-tracking branch 'origin/bov-feature-extraction' into bov-feature-extraction

Conflicts:
	conf/exp0/exp0_base.conf
	conf/exp1/exp1_base.conf
	conf/exp10/exp10_base.conf
	conf/exp11/exp11_base.conf
	conf/exp13/exp13_base.conf
	conf/exp14/exp14_base.conf
	conf/exp18/exp18_base.conf
	conf/exp19/exp19_base.conf
	conf/exp20/exp20_base.conf
	conf/exp21/exp21_base.conf
	conf/exp22/exp22_base.conf
	conf/exp23/exp23_base.conf
	conf/exp24/exp24_base.conf
	conf/exp25/exp25_base.conf
	conf/exp26/exp26_base.conf
	conf/exp27/exp27_base.conf
	conf/exp29/exp29_base.conf
	conf/exp30/exp30_base.conf
	conf/exp31/exp31_base.conf
	conf/exp32/exp32_base.conf
	conf/exp33/exp33_base.conf
	conf/exp34/exp34_base.conf
	conf/exp5/exp5_base.conf
	conf/exp6/exp6_base.conf
	conf/exp8/exp8_base.conf