WIP: Set kbas to be less restrictive on allowed filenames

ybd makes no attempt to escape filenames for the restrictions set by kbas, thus certain chunks can end up being built every time. Loosen restrictions set by the kbas regex to fix such cases:

[libdbus-c++] Starting upload
[libdbus-c++] Artifact server problem: 400
[libdbus-c++] Failed to upload libdbus-c++.joidja8

Fixes #256, the check now disallows control characters and / in filenames.