Minor corrections for DTPR Design Guide

[sevaan]

A little typo jumped out at me on Page 6, 7, 8, 9 of the DTPR_Design_Guide.pdf:

URL should be dTpr.dev

The URL can also been seen on the sample signage on Page 11:

Additionally, on Page 4 you recommend adding a short URL for users without QR code scanning abilities, but on Page 12 show a sign without any URL that may be worth correcting:

[sevaan]

The hexagons used in the design guidelines are different to the provided icons (which have more rounded corners).

[patrickkeenan]

All good points, we'll factor these into the next design guide rev.