Fix: MOUSE_UP action was ignored if any other mouse button was pressed

[ToTheHit]

Checklist

• [x] The code has been run through pretty yarn run pretty
• [x] The tests pass on CircleCI
• [x] You have referenced the issue(s) or other PR(s) this fixes/relates-to
• [x] The PR Template has been filled out (see below)
• [x] Had a beer/coffee because you are awesome

What? | Why?

https://github.com/projectstorm/react-diagrams/issues/940

How?

Store pressed mouse button and ignore other events if they contain different button. Also I did a little refactor, because 9 if-else is too much :)

Feel good image: