ordering of array messages in left sidebar

[scott-eddy]

Currently array messages in the left sidebar are grouped alphabetically, but the case where you have over 10 data fields in a message leads to strange ordering. E.G. you will have

variable_0
variable_1
variable_10
variable_11
...
variable_19
variable_2
variable_20

If the variable has the same name the ordering should be based on numbering

[facontidavide]

This is one of those use cases where a PR is welcome :)