Removing the need to use ‘Stop adding nodes’

[gargshashank5]

Currently when the user is adding nodes the add nodes button shows ‘stop adding nodes’ but he has to switch to adding edges he should be able to simply click on ‘start adding edges’. When the user clicks on ‘start adding edges’ and the ‘stop adding nodes’ button should automatically change to ‘start adding nodes’ and the user should be able to add the edges.

[e55k4y]

This has been implemented but the button status is simultaneously toggled. Please check the last commit.