Validation, settings UI cleanup and different settings models, oh my

New: Download client UI matches other settings
Fixed: Prevent drone factory folder from being set to invalid paths/root path for series
Fixed: Switching pages in settings will not hide changes
Fixed: Test download clients
Fixed: Settings are validated before saving

src/NzbDrone.Core/Validation/FolderValidator.cs

@@ -0,0 +1,19 @@
+using FluentValidation.Validators;
+using NzbDrone.Common;
+
+namespace NzbDrone.Core.Validation
+{
+    public class FolderValidator : PropertyValidator
+    {
+        public FolderValidator()
+            : base("Invalid Path")
+        {
+        }
+
+        protected override bool IsValid(PropertyValidatorContext context)
+        {
+            if (context.PropertyValue == null) return false;
+            return context.PropertyValue.ToString().IsPathValid();
+        }
+    }
+}

src/NzbDrone.Core/Validation/Paths/DroneFactoryValidator.cs

@@ -0,0 +1,29 @@
+using System;
+using FluentValidation.Validators;
+using NzbDrone.Common;
+using NzbDrone.Core.Configuration;
+
+namespace NzbDrone.Core.Validation.Paths
+{
+    public class DroneFactoryValidator : PropertyValidator
+    {
+        private readonly IConfigService _configService;
+
+        public DroneFactoryValidator(IConfigService configService)
+            : base("Path is already used for drone factory")
+        {
+            _configService = configService;
+        }
+
+        protected override bool IsValid(PropertyValidatorContext context)
+        {
+            if (context.PropertyValue == null) return false;
+
+            var droneFactory = _configService.DownloadedEpisodesFolder;
+
+            if (String.IsNullOrWhiteSpace(droneFactory)) return true;
+
+            return !droneFactory.PathEquals(context.PropertyValue.ToString());
+        }
+    }
+}

src/NzbDrone.Core/Validation/Paths/PathExistsValidator.cs

@@ -0,0 +1,23 @@
+using FluentValidation.Validators;
+using NzbDrone.Common.Disk;
+
+namespace NzbDrone.Core.Validation.Paths
+{
+    public class PathExistsValidator : PropertyValidator
+    {
+        private readonly IDiskProvider _diskProvider;
+
+        public PathExistsValidator(IDiskProvider diskProvider)
+            : base("Path does not exist")
+        {
+            _diskProvider = diskProvider;
+        }
+
+        protected override bool IsValid(PropertyValidatorContext context)
+        {
+            if (context.PropertyValue == null) return false;
+
+            return (_diskProvider.FolderExists(context.PropertyValue.ToString()));
+        }
+    }
+}

src/NzbDrone.Core/Validation/Paths/PathValidator.cs

@@ -0,0 +1,28 @@
+using FluentValidation;
+using FluentValidation.Validators;
+using NzbDrone.Common;
+
+namespace NzbDrone.Core.Validation.Paths
+{
+    public static class PathValidation
+    {
+        public static IRuleBuilderOptions<T, string> IsValidPath<T>(this IRuleBuilder<T, string> ruleBuilder)
+        {
+            return ruleBuilder.SetValidator(new PathValidator());
+        }
+    }
+
+    public class PathValidator : PropertyValidator
+    {
+        public PathValidator()
+            : base("Invalid Path")
+        {
+        }
+
+        protected override bool IsValid(PropertyValidatorContext context)
+        {
+            if (context.PropertyValue == null) return false;
+            return context.PropertyValue.ToString().IsPathValid();
+        }
+    }
+}

src/NzbDrone.Core/Validation/Paths/RootFolderValidator.cs

@@ -0,0 +1,24 @@
+using FluentValidation.Validators;
+using NzbDrone.Common;
+using NzbDrone.Core.RootFolders;
+
+namespace NzbDrone.Core.Validation.Paths
+{
+    public class RootFolderValidator : PropertyValidator
+    {
+        private readonly IRootFolderService _rootFolderService;
+
+        public RootFolderValidator(IRootFolderService rootFolderService)
+            : base("Path is already configured as a root folder")
+        {
+            _rootFolderService = rootFolderService;
+        }
+
+        protected override bool IsValid(PropertyValidatorContext context)
+        {
+            if (context.PropertyValue == null) return true;
+
+            return (!_rootFolderService.All().Exists(r => r.Path.PathEquals(context.PropertyValue.ToString())));
+        }
+    }
+}