Stubbed custom attribute adding via context menu

Made MPContextToolbarButton usable as normal button.
Added private API helper for adding buttons to NSUserNotification
Remove Autotype plugin API
Enhanced custom attribute plugin API
Enhanced EntryActionPlugin API to decouple menu items from actual action/target setup
Stubbed action on no-open documents NSUserNotifications
Stubbed HMACOTP custom attribute setup

MacPass/MPEntryInspectorViewController.m

@@ -43,6 +43,8 @@
 #import "MPActionHelper.h"
 #import "MPSettingsHelper.h"
 #import "MPPasteBoardController.h"
+#import "MPContextButton.h"
+#import "MPAddCustomFieldContextMenuDelegate.h"
 
 #import "MPArrayController.h"
 
@@ -67,6 +69,7 @@ typedef NS_ENUM(NSUInteger, MPEntryTab) {
   MPWindowAssociationsTableViewDelegate *_windowAssociationsTableDelegate;
   MPWindowTitleComboBoxDelegate *_windowTitleMenuDelegate;
   MPTagsTokenFieldDelegate *_tagTokenFieldDelegate;
+  MPAddCustomFieldContextMenuDelegate *_addCustomFieldContextMenuDelegate;
 }
 
 @property (nonatomic, assign) BOOL showPassword;
@@ -97,9 +100,12 @@ typedef NS_ENUM(NSUInteger, MPEntryTab) {
     _windowAssociationsTableDelegate = [[MPWindowAssociationsTableViewDelegate alloc] init];
     _windowTitleMenuDelegate = [[MPWindowTitleComboBoxDelegate alloc] init];
     _tagTokenFieldDelegate = [[MPTagsTokenFieldDelegate alloc] init];
+    _addCustomFieldContextMenuDelegate = [[MPAddCustomFieldContextMenuDelegate alloc] init];
     _tagTokenFieldDelegate.viewController = self;
     _attachmentTableDelegate.viewController = self;
     _customFieldTableDelegate.viewController = self;
+    _addCustomFieldContextMenuDelegate.viewController = self;
+    
     _activeTab = MPEntryTabGeneral;
   }
   return self;
@@ -166,6 +172,7 @@ typedef NS_ENUM(NSUInteger, MPEntryTab) {
   
   self.tagsTokenField.delegate = _tagTokenFieldDelegate;
   
+  [self _setupCustomFieldsButton];
   [self _setupViewBindings];
 }
 
@@ -542,6 +549,14 @@ typedef NS_ENUM(NSUInteger, MPEntryTab) {
   
 }
 
+- (void)_setupCustomFieldsButton {
+  /* FIXME: this is a bug in MPContextButton preventing the image set in IB to be used */
+  [self.addCustomFieldButton setImage:[NSImage imageNamed:NSImageNameAddTemplate]];
+  NSMenu *customFieldMenu = [[NSMenu alloc] initWithTitle:NSLocalizedString(@"ADD_CUSTOM_FIELD_CONTEXT_MENU", @"Menu displayed for adding special custom keys")];
+  customFieldMenu.delegate = _addCustomFieldContextMenuDelegate;
+  self.addCustomFieldButton.contextMenu = customFieldMenu;
+}
+
 #pragma mark -
 #pragma mark HNHUITextFieldDelegate
 - (NSMenu *)textField:(NSTextField *)textField textView:(NSTextView *)view menu:(NSMenu *)menu {