Fixed problem of chrashes on nvm/mec creation with fastboot enabled (#164)

* - BIOS in game config now is stored by name instead of full path, making it more portable

* - added check if bios folder is empty, logging in that case an explicit message

* fixed problem wich prevented to load selected memory cards when starting core without content

* removed a forgotten debug log

* disabled fast boot when entering bios menu

* forced to boot into bios setup also when fast boot enabled and if nvm not exists
2 jobs for main in 4 minutes and 7 seconds (queued for 2 minutes and 8 seconds)
Status Name Job ID Coverage
  Build Shared
passed libretro-build-linux-x64 #895856

00:02:20

passed libretro-build-windows-x64 #895855
msvc2019

00:01:47