Parser uses a function instead of a constant object to create empty property objects now.
Comment typos edited.
[Issue#6] Fix to handle case-insensitive key duplicates in properties object.
[Issue#8] Improvement implementation to avoid duplicate downloads for observed properties.

If multiple wfs:member -elements are included in the response XML, also om:observedProperty -elements are given multiple times in them for the query. Therefore, additional check was implemented to avoid duplicate downloads for same URLs.
[Issue#7] WfsConnection handles sites as case-insensitive strings when cache is used.

Server handles places as case-insensitive strings. Therefore, WfsConnection class was improved to compare given sites as case-insensitive strings when cache is used.
Fine tuning editing.
Release version 1.1.8