[xmlutils] use XMLUtils::GetAttribute() when assigning attributes directly to CStdString/std::string, as they may be NULL
[xml] fix potential null pointer dereference when reading attributes
[addons] make the 'type' attribute of addon settings consistently compared case-sensitive
[addons] read the id attribute into a std::string where comparison is made case-sensitive
[xml] use GetAttribute() where it makes the code clearer (and where used enough to warrant the include)
[xml] use TiXmlNode::Attribute(foo, int|double) method where it tidies things up
[xml] read attributes into const char* where they're re-used immediately
[skinsettings] setting type of skin settings needn't be compared case-insensitive (we write them, we read them)
[addons] have the 'subsetting' attribute and '' values attribute be case-sensitive to drop some strcmpi()
[settings] make the advancedsetting 'bydate' attribute for tvshow regexps case-sensitive (i.e. 'true')
[addons] drop duplicate if clause
[cosmetic] align assignment block