fixed validateNumber (now E.164)

Fixed validateNumber according to http://en.wikipedia.org/wiki/E.164#Telephone_number_categories
CHECKPOT! :tada:

I already checked the [ts-android](https://github.com/WhisperSystems/TextSecure/blob/master/src/org/thoughtcrime/securesms/util/NumberUtil.java) and [ts-iOS](and https://github.com/WhisperSystems/TextSecure-iOS/blob/master/TextSecureiOS/Contacts/TSContactManager.m) code, but both pass their number vertification to the corresponding andoird/iOS-APIs...

The [android source code](https://github.com/android/platform_frameworks_base/blob/master/telephony/java/android/telephony/PhoneNumberUtils.java) wasn't really illuminative, too.

However I just found [libphonenumber](https://code.google.com/p/libphonenumber/) which is the default lib for android 4.0+ and is also available as a js implementation!
Here's a demo: https://libphonenumber.googlecode.com/svn/trunk/javascript/i18n/phonenumbers/demo-compiled.html (notice that the country code is something like "US")

And, hey!, it's Apache License 2.0! Since we choose GPL **v3** [we can use this library](https://en.wikipedia.org/wiki/Apache_License#GPL_compatibility).

Using the library should be the right way to go. I'm going to implement all this (annoying) number verification stuff (in another branch) using the lib...