Descriptor check & Main Header locating

[5saviahv]

• added 32-bit descriptor field checking
• removed complement operator - it may give some false negatives due to javascript number variable length. Maybe related with Invalid or unsupported zip format. No END header found #268.
• added option "trailingSpace" - for allowing searching header from entire file. Extracting from Buffer with trailing zeros cause 'Invalid or unsupported zip format. No END header found' error #264