feature: unify how properties are defined (under_score to camelCase)

[elboletaire]

Describe the feature

The SDK uses under_scored and camelCased properties in objects without an apparent differentiation between them.

Motivation

To have a logical API, which is easy to follow and is congruent with all its definitions.

Proposal

Redefine all public under_scored properties to camelCased ones.

Components affected

• ClientOptions
• VocdoniSDKClient

And probably more, in general we should check every exposed object that is not a mapping interface/class (obviously those used for mapping may require underscore in some fields, but these usually are not publicly exposed to the developers [yes, they are exposed, but not "publicly"..]).

Constraints & Assumptions

This is a breaking change, so we may need to release a new major beta version (i.e. 0.2.0)