Fix #113 editor_settings.xml corruption

In the `parse_tag` method of the `class ResourceInteractiveLoaderXML`,
the class responsible of loading the editor_settings.xml file, the
properties' values are loaded directly into an `String` object but the
file contents are always UTF-8, which leads to garbage in the XML file
when saved.

This patch reads the properties' values in a `CharString` and translate
them to UTF-8.
Merge pull request #123 from Terseus/fix-113_editor-settings-xml-corruption

Fix #113 editor_settings.xml corruption