[FEATURE] Support greaterThan and lessThan for range filters

A range filter cannot be easily used in Eel expressions since the
TypoScript parser does not allow double nested curly braces for
now. The two new query builder methods expose a high-level interface
for doing that.
When reading this, $propertyValue is confusing. What is passed is the value to compare the property value to, so it should be named differently (also in the other added methods). The README.md uses just "value", which would be fine for the parameters as well IMHO.