Added all Zip compression names from 6.3.3 format

I've added all the compression names and IDs from the ".ZIP File Format
Specification" version 6.3.3  that can be found in section "4.4.5
compression method" of this document:

http://www.pkware.com/documents/casestudies/APPNOTE.TXT
Simplified and fixed Zip compression method array

I've removed the description string element from the compression_method
struct and fixed some spelling errors (imb -> ibm).
Removed compression_method struct type

Since it was only used in one place, I've remove the struct type.
Merge pull request #48 from kwk/master

Added all Zip compression names from 6.3.3 format