Review immutable vs constant vars + ordering in vault

[hieronx]

          1. I think there should be consistency. One is initialized  in the variable declaration an some in the constructor. I think it should be in one place.

2. Naming should be also unified and I see some parts of the solidity style guide were followed and some not. We can agree of course on this :)
3. I was curious why you would choose constructor initialization over in declaration so I deployed 2 version of the same contract ( on Remix ) .

• Version 1: All variables marked as constants and initialized during declaration
• Version 2: All variables immutable and initialized in the constructor
  Version 2 deployment cost was less than the Version deployment cost.

I don't know why it's that. it's just an observation.

Originally posted by @peculiarity in #308 (comment)