Fix SC1000: `$` is not used specially and should therefore be escaped.
Fix SC2003: `expr` is antiquated. Consider rewriting this using `$((..))`, `${}` or `[[ ]]`.
Fix SC2004: `$` on variables in `(( ))` is unnecessary.
Fix SC2045. Iterate over globs whenever possible.

Iterate over globs whenever possible (e.g. 'for f in */*.wav'), as for
loops over ls will fail for filenames like 'my file*.txt'.
Fix SC2120.

`__apt_get_upgrade_noinput` references arguments, but none are ever passed.
Fix SC2091. Remove surrounding $() to avoid executing output.
Fix SC2059. Don't use variables in the printf format string.

Use printf "..%s.." "$foo".
Merge pull request #358 from s0undt3ch/develop

Several Lint Fixes