Custom upload server: More checks for upload readiness

Merge pull request ruslo#1805 from ErniBrown/pr.zmqpp

Added zmqpp version 4.2.0

tvm 0.5-p4

mxnet 1.4.0-p2

Merge pull request ruslo#1801 from dvirtz/pr.cmcstl2

add cmcstl2

Add autogenerated

Update lehrfempp to 0.7.18 (ruslo#1799)

Merge pull request ruslo#1798 from chfast/pr.snappy

Upgrade Snappy to v1.1.7

Merge pull request ruslo#1797 from bkotzz/pr.bento4

Add 'Bento4' package

Merge pull request ruslo#1796 from dvirtz/pr.range-v3.update

update range-v3 to 0.4.0-01ccd0e5-p0