inconsistent naming conventions

[matyb]

variables and method names are too generally named, or are so short that they could be confusing or lack the expressiveness they could have. examples:

• remove converter interface, and expose specific (more explicitly named) conversion methods
• stringbuilder named string, something more specific and less misleading would be better
• toNumber, etc. should be more explicitly named
• other misleading, awkward or overly terse naming should be clarified

[matyb]

elaborated overly terse or misleading names, eliminated overly generic converter interface
see commit 29d98be for details