Fixup types in rlm_couchbase instance struct, and add type validation
Add PW_TYPE_SIGNED and PW_TYPE_INTEGER64 to the conffile parser

PW_TYPE_INTEGER was being used to create signed ints, which in the vast majority of places was wrong (they needed unsigned ints).

For anything which does need signed ints there's now PW_TYPE_SIGNED.
Add a few more enum types
Pass pointer to the handle instead of handle in SQL group functions