Upgrade the ASCII type to fit with the new model for netzob types
ASCII type includes constraints definitions that are considered in the generate and canParse methods.
New Type model with constraints and value.

An instance of a netzob type is now required to define the definition domain
of a field. This domain can have a specific value and/or some constraints.
New implementation of the BitArray to support new Type model.

The BitArray definiton includes a constraints over the number of bits.
Upgrade Decimal type to comply with the new type model.
WIP over the HexaString new implementation.
New version of the IPv4 to comply with the new type model.

An IPv4 definition domain can represents either a specific IPv4 or a range of IPs.
New version of the Raw type to comply with the new Type implementation.
Add some additionnal information when requested type is not available for conversion
Upgrade the definition of ApplicativeData.
Fix docTests in AbstractVariable to comply with the new definition domain definition
First check if format is compatible before executing the forget operation over a variable
No more constraints (size) in the Data definition, see the new Type definition.
Rename toString method to __str__ method
Update docTests in Field to comply with the new Type model.
The dataType value is an instance and not anymore a class
Fix various docTests to comply with new type model
Update to comply with the new type model