v0.18 : Introduce UserReader

Introducing a new more usable reader was accomplished, making it easier for fire to be fully used by ldmx-sw. Along the way of alpha-testing within ldmx-sw, I also introduced some more headers and other inter-op mechanics to make the switch easier on ldmx-sw.

What's Changed

• ldmx-sw Interop by @tomeichlersmith in #49
• user file reader by @tomeichlersmith in #50

Full Changelog: v0.17.0...v0.18.0