fix naming inconsistencies between binaries and signature files

[chaserene]

all .sig files in signatures-1.7.5.zip (except for the .sig for the .deb package) have a white space ("Zecwallet Lite") instead of a period that is used in the binary releases ("Zecwallet.Lite"). this yields a bad signature check result when the .sig is placed in the same folder. the names should match for he check to pass. you can rename the file, but you first need to figure this out.

as an aside, to avoid similar problems, I suggest using a single separator (the dash is a good one) in all binary names and using only lowercase letters.