basic.py: update retroarch-joyconfig path

Use the new file location like https://github.com/petrockblog/RetroPie-Setup/commit/3e029a9e2f453809723cd1847716f0d36b38e631.
Merge pull request #521 from gizmo98/patch-1

basic.py: update retroarch-joyconfig path
take a single parameter for ram in rpSwap - the total needed ram - rpSwap will calculate how much additional swap is needed
calculate toal memory just before adding additional swap just in case anything has changed since the script started (such as manually added swap, or in the case the script was interrupted and an old swap was still active)
use 750mb total ram for mupen64/libretro emulator - as upstream requests
Merge remote-tracking branch 'upstream/master'
removing pi-specific packages
when cloning EmulationStation, do not --depth=1

this allows us to check out the unstable branch correctly.