Bug 838040 - allow access of bookmark menu from the bookmark tab

Change to new approach to avoid the browser.param and also solved Homescreen button showing problem. 

Approach (thanks advice from @timdream):

Since `showBookmarkMenu` is bind to bookmark page, I add `showBookmarkTabContextMenu` function to handle contextmenu in bookmark tab,
and move actual menu-showing function to a new `showActionMenu` function.

 `showActionMenu` function have two params:

with `url` param, `showBookmarkMenu` & `showBookmarkTabContextMenu` can pass correspondent url to `showMenu` function. 

with `from` param, showActionMenu can customize the item to show in ActionMenu.

In `showActionMenu`, append `bookmarkMenuRemove.dataset.url` params to the button. 

So  in `removeBookmark` function. we can process url from button dataset instead of parsing `this.currentTab.url`.