Make compatible with non-bash shells, etc— portability changes

[JadedCtrl]

These are just a few changes that make it so the script can run on basically any system— curl or wget used can be used, sha256 or sha256sum can be used, and all arrays are replaced with simple strings.

(Arrays are a bashism that can be useful sometimes, but aren't usually necessary. Here, since every item in the arrays were only one word long, iterating through the string works perfectly, since space is the default delimeter.)

[sigmaboy]

@JadedCtrl Sorry for answering this late. Will have a look the next few days and merge it. Looks good so far

[sigmaboy]

@JadedCtrl Thank you very much.