Chart is broken in group tab

[Halleck45]

In 2.7.3, MI chart does not display due to #430

We need to revert this PR

[niconoe-]

This is mainly because the js variable "classes" is redefined, IMO. Why not declaring, and using, a different variable for layer groups?

EDIT: after a deeper analysis, the problem is bigger: For each layer group + general, all templates are reused, but without any variabilisation of unique stuff, so HTML ids are duplicated, such as js global variables and so...
We need to detect all duplicated that can't be and variable them using the group name or a group index to remove conflicts

[pattisahusiwa]

@Halleck45, can you show a picture about the broken chart? or give more explanation about that. I can't reproduce the bug.

[Halleck45]

Hi @pattisahusiwa . When you click on the tab of specific group, the maintainability chart does not load due to JavaScript issue.

I think that #437 fixes the issue