Add grid system

[MarcinKasprowicz]

Notes:

• Click on the button changes grid between 1, 2, 3 columns per row.
• Graph shrinking/expanding - I left this as it is, hiding graphs help with performance -> remaining graphs will is smoother.
• Switching between graphs is enabled only when at least two functions are monitored.
• For smaller screens (below 1280px) max grid is 2 columns (when user will change the size of the browser below this value it will not automatically resize from 3 to 2 - edge case, I didn't want to implement that - laziness 🐵)

closes #117

[gomoripeti]

LGTM

• Graph shrinking/expanding - I wanted to complain about this (why would someone want to collaps just one graph in a row) but the performance consideration convinced me

• maybe I would like a bit smaller icon better (and maybe the bg could be same as the magnifier-search in the navbar) but after I started playing with the css, I was convinced that this looks perfectly fine as is

• maybe the buttons could have tooltips (I realise none of them have)