Fixes ResourceOracleImplTest by restoring class path entry get/set for all AbstractResources.

Also added a non-classpath constructor for ZipFileResource to work with zip libraries.

Change-Id: I8d9fa84f48e4c84503aad38d61832b2623cb5464
Implements UrlResource to adapt URL instances to the Resource interface

This is useful when copying data that was not loaded via the normal
resource system (for example .gwt.xml files) into systems that expect a
resource object (for example a library builder).

Change-Id: Ife9907407399d728ce29bf9a40a24d1b421cb1eb
Adds a visitor capable of collecting reboundTypes even in an AST
that has not yet been unified.

In monolithic compilation the act of AST unification and GWT.create()
rebinding were combined in UnifyAst. But with separate compilation
these steps need to be separate and thus the need for a rebound type
collection process that can function even prior to unification.

Change-Id: Iaeb55573c9942cc864639ed7c6d91f736d15cfdb
Revert "Implements UrlResource to adapt URL instances to the Resource interface"

This reverts commit 88c5fc49eb4526f1780f183e3ce9826fd378aa02.

Change-Id: I7b6004c7c1812da74e22e4d871cc1d12415825a2
Adds a "combined" resource oracle view of multiple other oracles.

Useful when the resource oracles being combined are very different
in nature. For example one that surfaces resources on disk for a
module and one that surfaces resources in a set of precompiled
libraries.

Change-Id: Ic7da3168c40bb6a24da1b4fa47787e032f97fff2
Review-Link: https://gwt-review.googlesource.com/#/c/4983/
Implements UrlResource to adapt URL instances to the Resource interface

This is useful when copying data that was not loaded via the normal
resource system (for example .gwt.xml files) into systems that expect a
resource object (for example a library builder).

Change-Id: Ida7a44e59519d11e10453bd0e3c1c9901f2bed0b