log in/log out rewrite

Delete network object after logging out. related to #262
Support for multiple log in. related to #263 
Activate the tab if we already have one open and catch tab is closed #328 
Close a tab if user denies access #475 

I'll follow up with cl fixing storage state.
I think we should also add a sanity check like
```
if (tabId != this.tabId_) {
  return;  // Ignore update event for other tabs
}
```