Room: Inform user when they cannot post to a room because of low power level

Create DisabledRoomInputToolbarView for such permission issue

Riot/Views/RoomInputToolbar/DisabledRoomInputToolbarView.m

@@ -0,0 +1,66 @@
+/*
+ Copyright 2018 New Vector Ltd
+ 
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+ 
+ http://www.apache.org/licenses/LICENSE-2.0
+ 
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import "DisabledRoomInputToolbarView.h"
+
+#import "RiotDesignValues.h"
+
+@implementation DisabledRoomInputToolbarView
+
++ (UINib *)nib
+{
+    return [UINib nibWithNibName:NSStringFromClass([DisabledRoomInputToolbarView class])
+                          bundle:[NSBundle bundleForClass:[DisabledRoomInputToolbarView class]]];
+}
+
++ (instancetype)roomInputToolbarView
+{
+    if ([[self class] nib])
+    {
+        return [[[self class] nib] instantiateWithOwner:nil options:nil].firstObject;
+    }
+    else
+    {
+        return [[self alloc] init];
+    }
+}
+
+#pragma mark - Override MXKView
+
+-(void)customizeViewRendering
+{
+    [super customizeViewRendering];
+    
+    // Remove default toolbar background color
+    self.backgroundColor = [UIColor clearColor];
+    
+    self.separatorView.backgroundColor = kRiotAuxiliaryColor;
+
+    self.disabledReasonTextView.font = [UIFont systemFontOfSize:15];
+    self.disabledReasonTextView.textColor = kRiotPrimaryTextColor;
+    self.disabledReasonTextView.tintColor = kRiotColorGreen;
+    self.disabledReasonTextView.editable = NO;
+    self.disabledReasonTextView.scrollEnabled = NO;
+}
+
+#pragma mark -
+
+- (void)setDisabledReason:(NSString *)reason
+{
+    self.disabledReasonTextView.text = reason;
+}
+
+@end