Update .get_search_query() to accomodate multiple values of 'q'

[typonaut]

Updated .get_search_query() to deliver a list via .getlist() rather than a string via .get() in order to accomodate multiple values of 'q', for example from forms.MultipleChoiceField() and/or forms.CheckboxSelectMultiple widget.

Updated .get_words() to expect a list rather than a string.

Added .strip_list() to replicate previous behaviour.