Feature/rename hd

 This is just a some maintenance renaming of function, classes and variables, aimed to keep
coherence in the code.

- variables were changed to camelCase
- class Structure changed to HDPath
- class AddressIndex to HDParams

- no changes where made on the networking protocol.
- some storage keys have changed on the backups, but its backwards compatible. Tests were added.
- mocha / karma test were updated and all OK.