This fixes the remaining problem within #615 wherein the displayed BPM range for songs that had different BPM ranges per-chart was incorrect.

619#issuecomment-520270829 the Lua binding for BPMDisplay `SetFromSteps` still did not work even after that change.

That was because BPMDisplay::SetBpmFromSteps did all the work to determine the correct BPM range and then just ... didn't call SetBPMRange to actually update it.

This PR fixes that function and then makes the simple changes required to Rebirth, Til Death, and bare-frames to get them to use it.

Closes: #615

etternagame / etterna

Fix incorrect bpm display for ssc songs with varying bpms per-chart #1217

619 fixed most of the problems, but as Poco noted in https://github.com/etternagame/etterna/pull/619#issuecomment-520270829 the Lua binding for BPMDisplay `SetFromSteps` still did not work even after that change.

etternagame / etterna

Fix incorrect bpm display for ssc songs with varying bpms per-chart #1217

619 fixed most of the problems, but as Poco noted in https://github.com/etternagame/etterna/pull/619#issuecomment-520270829 the Lua binding for BPMDisplay SetFromSteps still did not work even after that change.

619 fixed most of the problems, but as Poco noted in https://github.com/etternagame/etterna/pull/619#issuecomment-520270829 the Lua binding for BPMDisplay `SetFromSteps` still did not work even after that change.