079cf88c0d refactor: move Boost datetime usage to wallet (fanquake)
Pull request description:
This means we don't need Boost Datetime in a `--disable-wallet` build, and it isn't included in the kernel (via time.h/cpp). Split from a larger boost removal branch/effort.
ACKs for top commit:
hebasto:
re-ACK 079cf88c0d
aureleoules:
re-ACK 079cf88c0d - rebased and two additional unit tests since my last review.
jarolrod:
crACK 079cf88c0d
Tree-SHA512: c84f47158a4f21902f211c059d8c4bd55ffe95a256835deee723653be08cca49eeddfc33a2316b0cd31805e81cf77eaa39c6c9dcff4cda11a26ba4c1c143974e