LIKE operator is case-sensitive, docs say case insensitive

Our documentation incorrectly states that the the LIKE operator is case-insensitive and the REGEX operator is the case-sensitive alternative.

As per https://github.com/couchbase/couchbase-lite-core/issues/296 which points out that due to nuances with collations, the LIKE operator in Couchbase Mobile 2.0 behaves in a case-sensitive manner.

The documentation should be updated to reflect this, though we would need to ensure that both the LIKE and REGEX sections are cohesive.
When the improvements come in 2.1 or 2.2 and we have an option for case-insensitive, these sections should be reviewed again.