Remove unused leading_zero_possible field from phonemetadata.proto

Deleted all methods that refer to this.
Regenerated jars - because we no longer write a boolean for the removed proto field, all the java metadata files needed regenerating too.

* Java and CPP port fixes.

* Js port update and added code changes notes.

* Updated text in code changes comments file.

This hasn't been used for a long time.
Deleted all methods that refer to this, and removed the field from the test XML file (somehow this was missed) as well.
Regenerated jars - because we no longer write a boolean to indicate whether we have the possible number pattern or not all the java metadata files needed regenerating too.
Deleted some data from the js phone metadata implementation that isn't used by js as well (national number matcher pattern)

*   It was confusing and unnecessary. Not every country that has short numbers beginning with a 0 had it, and it is not the only digit that could overlap with a national prefix and hence be interpreted incorrectly.

1) Changing the BuildMetadataFromXml to only set
same_mobile_and_fixed_line_pattern and
national_prefix_optional_when_formatting if they differ from default
values, and the domestic_carrier_code_formatting_rule,
international_prefix and national_prefix_formatting_rule if there is
one.

2) Adding a test with some golden data for the BuildMetadataJsonFromXml.

3) Adding to the proto a missing explicit default false.

4) Updating a couple of methods in the Phonemetadata.java class to have
names that match those of the auto-generated Phonemetadata used by the
CPP build, now that we use those methods when building the metadata.

5) Fix to ant build file to enable the junit command to still work (instructions on open-source on how to regenerate metadata files refer to this)

Resulting data is smaller for Java and C++ and the resulting BuildMetadataJsonFromXml code is cleaner.

Update doc references to refer to CLDR and the page of CLDR codes where
appropriate - it used to say ISO country codes were used, but they aren't.

Also updated to refer to two *or three* letter language codes since they may be three letters (we use the shortest defined one for a language)

Updating comments about leadingDigits field at territory level as well.

https://groups.google.com/forum/#!topic/libphonenumber-discuss/75TOpTFVi08

* Initial code changes to support the new possibleLengths infrastructure
when building metadata. Includes setting these in the main metadata
file and changing the code to populate them in the PhoneMetadata proto
at build time. Updating tests for Java.

* Updating comment about the possible_lengths_local_only field.

* Adding the generated jars that build files containing the new possible
lengths fields.

* Rebuilding short-number metadata with the new proto field. Not doing
this at release time so we can see what changes in the metadata are due
to metadata fixes, rather than this possibleLengths field.

* Regeneration of phone number metadata with the new possible length
information filled in.

Includes some possible length changes for KR and BY, and a validation
fix for NA where a digit was missing.

* Updating the test proto metadata files with the new possible length
information.

* Added notes about the code changes.

* Regenerating C++ metadata with new possibleLength info and updating unit
test to check this works.

No change in functionality.