Load ‘settings.lua’ as part of the standard includes

The file ‘standardIncludes.lua’ contains all of the modules we want to
load most of the time.  For example, it loads the ‘graphics’ module.
But that ‘graphics’ module expects us to have loaded the ‘settings’
module first, which we do not do.

This patch loads the settings first in the standard includes so that
‘graphics’ has access to it, and removes the

    require("src.settings")

expression from the ‘main.lua’ source since it is now redundant.
Rename files to fix case-sensitivity errors on Linux

The game fails to run on Linux because LÖVE complains about
‘mainmenu.lua’ not being the same as ‘mainMenu.lua’, because I would
ever want two files in the same directory that were only different
based on their case, for fuck’s sake….

This patch changes the requires and filenames that LÖVE complains
about on Linux so that the game will run.
Merge branch 'ejmr/fix-standard-includes'

* ejmr/fix-standard-includes:
  Rename files to fix case-sensitivity errors on Linux
  Load ‘settings.lua’ as part of the standard includes