Add more customization to variables.

[fabean]

It would be nice to allow people to change more settings like what grids they want, maybe they never will use 1-12, so why include it.

Others:

• flex-grow default: allow for flex: 0 0 100%;

[fabean]

You can now edit the amount of columns in the Grid and adjust grow and shrink by variables now.

You still cannot turn off 1-12 or things like that by variables.