Repoint dictionary / stopwords for v1 to v2 conversion

[joeytakeda]

Following from #359, we are considering using the same strategy for repointing the dictionary and stopwords files. E.g. we could check if the dictionary and stopwords used to point to $STATIC_SEARCH_DIR/xsl/english_stopwords.txt, and, if so, replace the value with $PATH_FROM_CONFIG_TO_STATICSEARCH/stopwords/stopwords_en.txt

[joeytakeda]

We should consider whether we ought to check for the existence of the old ones and, if they aren't there, then repoint (to accomodate people who may, for whatever reason, keep those files in the folder and had edited them in place).