Refactor plotting JavaScript

[ewels]

Merged three issues into this:

1. Currently, if samples are hidden in the saved config, the page loads then is immediately unresponsive whilst those samples are removed.
2. Highlight line graphs samples - save doesn't work (Highlight line graphs samples - save doesn't work #54)
3. Speed up 'hide samples' (Speed up 'hide samples' #53)

Most of the toolbox features currently work on rendered plots - looking through existing features and changing them. Instead, it might be better to replot everything when something changes.

• Restructure plotting functions to work off a canonical data source that doesn't change
  • Make a copy of this data at plot time
  • Get highlight / rename / hide settings from page
  • Recolour / rename / remove data from the copied data structure
  • Create plot
• Refactor highlight / rename / hiding to call plotting functions when changed, instead of modifying directly
• Plotting functions should not fire on page load, instead be triggered by config load.

This is sort of semi-implemented already in some places, for instance all of the code involving sample renaming. This is a fairly large refactoring, but I think that it will make the reports quite a bit more stable.

It could also lead to a potential fix for the mysterious slowness in #53, as hiding samples often seems slower than opening the page in the first time.

Finally - it should also fix #54 as the sample colouration will be set properly in the highcharts settings, so properly exported in other file formats (rather than a post-plotting hack).