Adds support for ePubs with large resources that don't fit into memory.

Conflicts:

	epublib-core/src/main/java/nl/siegmann/epublib/domain/Resource.java
Otpimized the way the zip entry of a lazy loaded Resource is found in the epub file.

Conflicts:

	epublib-core/src/main/java/nl/siegmann/epublib/domain/Resource.java
Merge pull request #49 from pparlev/master

Support for very large epub files.