Make goog.fs.* classes and goog.testing.fs.* classes implement common interfaces to allow typechecking to work when compiling tests that use the latter.

Prior to this CL we had:

goog.fs.Entry (concrete class)
goog.fs.FileEntry (subclass of goog.fs.Entry)
goog.fs.DirectoryEntry (subclass of goog.fs.Entry)

goog.testing.fs.Entry (concrete class)
goog.testing.fs.FileEntry (subclass of goog.testing.fs.Entry)
goog.testing.fs.DirectoryEntry (subclass of goog.testing.fs.Entry)

With this CL, this is changed to:

goog.fs.Entry (interface)
goog.fs.DirectoryEntry (sub-interface of goog.fs.Entry)
goog.fs.FileEntry (sub-interface  of goog.fs.Entry)
goog.fs.EntryImpl (concrete class, implements goog.fs.Entry)
goog.fs.DirectoryEntryImpl (subclass of BaseEntry, implements goog.fs.DirectoryEntry)
goog.fs.FileEntryImpl (subclass of BaseEntry, implements goog.fs.FileEntry)

goog.testing.fs.Entry (concrete class, implements goog.fs.Entry)
goog.testing.fs.DirectoryEntry (subclass of goog.testing.fs.Entry, implements goog.fs.DirectoryEntry)
goog.testing.fs.FileEntry (subclass of goog.testing.fs.Entry, implements goog.fs.FileEntry)
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=46470890
CLDR 23 data update (also Spanish first day of week, Palestine)
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=46567712
Fix small bugs in handling of module base URLs.
- Remove ".js" as a suffix of the base URL, not as a substring.
- Allow applications to set the base URL to an empty string.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=46570392
Changes linkbubble test to test for null using assertNull rather than trying to fire on a null element.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=46612898