theme bootstrap override asset not copied on install

[craigh]

if a theme declares a bootstrap override path in theme.yaml then that asset should be copied to public on install or it will not be available when needed.

refs #4366

[craigh]

another option is to require the override path be stated in "zasset" notation e.g. @AcmeFooModule:css/myCustomBootstrap.css

craigh/SimpleScrollTheme@74f2db6

[craigh]

another option is to require the override path be stated in "zasset" notation

since this would require a change in the Api expectation and break existing themes, this cannot be the current solution.

requiring this change could be done for 4.0.0 though.