Upgrade FPDI
This is the same as the first 2 commits of !141 (closed) (cherry-pick actually works!). I think this will fail and then I'll need to update the pdf with 2 bytes again.
Upgrades to 2.x to address #120 (closed), which is a bit of a rewrite but we only use it in one place and only use 3 functions that haven't changed, and it removes the need for the tcpdf workaround in #110 (closed).