Fix the '--bundle-dup-excludes' flag and add '--bundle-dup-max-dups'

Now the default output prints out how many more you get:

   Duplicate classes and/or resources detected in artifacts: (u'commons-beanutils-commons-beanutils-1.7.0.jar', u'commons-beanutils-commons-beanutils-core-1.8.0.jar')
                        org/apache/commons/beanutils/BeanAccessLanguageException.class
                        org/apache/commons/beanutils/converters/URLConverter.class
                        org/apache/commons/beanutils/locale/converters/IntegerLocaleConverter.class
                        org/apache/commons/beanutils/converters/CharacterArrayConverter.class
                        org/apache/commons/beanutils/MethodUtils.class
                        org/apache/commons/beanutils/converters/BooleanConverter.class
                        org/apache/commons/beanutils/converters/ClassConverter.class
                        org/apache/commons/beanutils/DynaBean.class
                        org/apache/commons/beanutils/converters/BooleanArrayConverter.class
                        org/apache/commons/beanutils/Converter.class
                        ... 123 more ...

Testing Done:
I've got a lot of duplicate classes on the classpath to sort out...

devpants goal bundle <target> --bundle-dup-max-dups=50 --bundle-dup-excludes=dependencies,license,notice,.DS_Store,notice.txt,cmdline.arg.info.txt.1,license.txt,org.apache.hadoop.fs.FileSystem,BCKEY.DSA,BCKEY.SF,ASL2.0,javax.servlet.ServletContainerInitializer,about.html

Bugs closed: 332

Reviewed at https://rbcommons.com/s/twitter/r/656/
Fix depmap to be able to see past a Dependencies target.  We use dependencies() liberally to create short aliases users can use to build common targets.

Testing Done:
Added some unit tests to test_depmap.py

Bugs closed: 242, 336

Reviewed at https://rbcommons.com/s/twitter/r/661/
Merge remote-tracking branch 'pants/master' into manifest_parser
Add BadManifestError to catch malformed or incomplete manifests

This error would eventually cause problem sin the compilation
process, but since we are parsing the manifest here, uncaught
exceptions would appear to be pants-related problems, as opposed
to an issue with their Android project.