Store state of hide lines and hide grid

[ImLucasBrown]

Make a user pref that stores the state of "hide lines" and "hide grid" actions.

[MichaelAldrich]

For record's sake. Hiding the grid is already stored here:

nxt_editor/nxt_editor/actions.py

Line 1189 in 2a52afd

self.grid_action = BoolUserPrefAction('Toggle Grid',

and the "hide lines" action is immediately below it, and can be fixed using the same BoolUserPrefAction probably.