properly quote GCC version string in archived easyconfig, fix issue with --repositorypath not honoring --prefix

I'm also renaming the archived easyconfigs here, to include the software name in the filename too (i.e. use `<repositorypath>/GCC/GCC-4.8.3.eb`  rather than `<repositorypath>/GCC/4.8.3.eb`

@geimer: this should fix #961, please verify?