luci-app-ddns: rollup to 2.3.0 to reflect changes on ddns-scripts

- support for new options "lookup_host", "param_enc" and "param_opt"
- rewritten ddns provider handling to only show/check needed options "domain", "username", etc.
- modified version check/handling incl. using new ipkg.compare_versions function
- modified map.title and map.description generation
- changed XHR.poll interval to 15 seconds on system status page
- using new value_parse function for testing and later implementation into cbi.lua
- some optimizations

Signed-off-by: Christian Schoenebeck <christian.schoenebeck@gmail.com>