SeqQC: .is(':visible') needs to be refactored where possible

[jmtcsngr]

Using $.is(':visible') has proven to be considerably slow when applied to a significant number of objects. Re-factor where possible as css rules so is not executed inside loops. We suspect it traverses the DOM each time it is executed to find if the element and its parents are part of subset of elements in the DOM (visible ones). An example of this situation is the code which generates d3 plots. The problem seems to be significantly worse with firefox.

[jmtcsngr]

$ git grep -n -i "is(':visible')"
npg_qc_viewer/root/static/scripts/plots.js:38:      if ( self.is(':visible') && self.children().length === 0 ) {
npg_qc_viewer/root/static/scripts/plots.js:68:      if ( self.is(':visible') && self.children().length === 0 ) {
npg_qc_viewer/root/static/scripts/plots.js:104:      if ( self.is(':visible') && self.children().length === 0 ) {