Adds functionality to allow for renaming of tags.

Towards #374

Signed-off-by: Abijeet <abijeetpatro@gmail.com>

ElectronClient/app/gui/MainScreen.jsx

@@ -145,6 +145,28 @@ class MainScreenComponent extends React.Component {
 					}
 				},
 			});
+		} else if (command.name === 'renameTag') {
+			const tag = await Tag.load(command.id);			
+			if(!tag) return;
+
+			this.setState({
+				promptOptions: {
+					label: _('Rename tag:'),
+					value: tag.title,
+					onClose: async (answer) => {
+						if (answer !== null) {
+							try {
+								tag.title = answer;
+								await Tag.save(tag, { fields: ['title'], userSideValidation: true });
+							} catch (error) {
+								bridge().showErrorMessageBox(error.message);
+							}
+						}						
+						this.setState({promptOptions: null });
+					}
+				}
+			})
+		
 		} else if (command.name === 'search') {
 
 			if (!this.searchId_) this.searchId_ = uuid.create();

ElectronClient/app/gui/SideBar.jsx

@@ -250,6 +250,21 @@ class SideBarComponent extends React.Component {
 			);
 		}
 
+		if (itemType === BaseModel.TYPE_TAG) { 
+			menu.append(
+				new MenuItem({
+					label: _('Rename'),
+					click: async () => {
+						this.props.dispatch({
+							type: "WINDOW_COMMAND",
+							name: "renameTag",
+							id: itemId
+						});
+					},
+				})
+			);
+		}
+
 		menu.popup(bridge().window());
 	}