[Contracts] optimisations

[bitbeckers]

As a Solidity developer, I want to evaluate the contracts to implement gas cost optimisations so that execution of contract calls becomes cheapers.

End of milestone V0.1

• [x] Inspect gas reported
• [x] E.g. refactor loops
• [x] Inspect mappings and structs
• [x] Review uint ranges
• [ ] Memory/calldata
• [ ] Variable packing
• [x] Gas cost looping over structs passed between methods
• [x] Split parse from mint for more flexible updating
• [ ] ...

[moconnell]

inlining the unpack data fn does appear to save smol amt gas

pre:

post:

[bitbeckers]

Gas at start of PR