allow external SD card storage; cleanups

[ollo22]

This PR allows revancify users to set the apk target folder, via

internalStorage=/storage/XXXX-XXXX ~/Revancify/revancify

It also cleans up some problematic code, though plenty of it remains. I'll point this out in separate GH issues.

If the authors are interested, this could be further developed (i.e. add a command-line switch, and update user-facing messages to reflect the actual storage location).

[decipher3114]

Repeated ping is an intended behaviour which checks internet everytime the user tries to access any option that requires internet.

Declaring it once may not cover up the cases in which the internet is not available after launching it.

[ollo22]

Fine, I can revert the ping. Perhaps factor it into a function, configurable via some CLI switch.

The problem is that on my phone, a simple ping -c 1 google.com; ping -c 1 google.com often hangs at the second ping. So the repeated checks often make revancify think the net is down. Moreover, one could argue that, even with repeated checks, the net could go down between the ping-check and the actual network op.