Changed feed parsing from python lib to RSXML

- Bug fix: Changing url to malformed one will remove all entries
- Bug fix: Add feed without selection resulted in a crash
- Removed FeedTag from database model

baRSS/FeedDownload.h

@@ -21,7 +21,8 @@
 //  SOFTWARE.
 
 #import <Cocoa/Cocoa.h>
+#import <RSXML/RSXML.h>
 
 @interface FeedDownload : NSObject
-+ (void)getFeed:(NSString*)url withBlock:(nullable void (^)(NSDictionary* result, NSError* error))block;
++ (void)getFeed:(NSString *)url block:(void(^)(RSParsedFeed *feed, NSError* error, NSHTTPURLResponse* response))block;
 @end