Improve caching of components inside cdist

[maxbachmann]

Currently cdist uses the following architecture:

for row in rows:
    cache = CreateCommonObjects(queries[row])
    for col in cols:
        cache.ratio(choices[col])

This works fine as long as cols is big. However, in a worst case cdist is called with a single choice. In this case creating the cache introduces a lot of overhead. It would make sense to create the cache for the cols in this case:

for col in cols
    cache = CreateCommonObjects(choices[col])
    for row in rows:
        cache.ratio(queries[row])