Add possibility to use comments in scenario files

This change allows to add comments to all scenario files (components.csv, el_grid.csv, commdata.csv as well as profiles) by starting the line with at least one #.

Question to resolve before merge: Is '#' a meaningful value in commdata.csv?

Example: components.csv

1,Slack,20000
2,Transformer,0,0,0,20000,400,19.2,61.0521088906845,250000,2,5
3,Node,2,0,0,400.0
# Nodes
## First Feeder
4,Node,2,0,0,400.0
5,Node,2,0,0,400.0
6,Node,2,0,0,400.0
7,Node,2,0,0,400.0
8,Node,2,0,0,400.0
9,Node,2,0,0,400.0
## Second Feeder
10,Node,2,0,0,400.0
11,Node,2,0,0,400.0
12,Node,2,0,0,400.0
13,Node,2,0,0,400.0
14,Node,2,0,0,400.0
15,Node,2,0,0,400.0
16,Node,2,0,0,400.0
# Components
## Loads
17,Load,SFH,1,1,1,1000,0.92
####thisalsoworks
# #   ## And those two are fine as well
#
...