Add the Change contract holder wizard

This first iteration we implement the more basic change holder logic. This wizard finish the selected contract and create a new with the same data and setting the data selected in the wizard. By now we can select:

Name	Label
delivery_mobile	Adreça enviament SIM
delivery_internet	Adreça enviament Router
internet_address	Adreça servei Internet
contact_address	Adreça de contacte
contact_email	E-mail contacte
party	Tercer
receivable_bank_account	Compte bancari a cobrar

With the end_date we generate the:

Name	Label
start_period_date	Data inici període
first_invoice_date	Data primera factura

And we get from the old contract the next information:

Name	Label
service_type	Tipus de servei
freq	Freqüencia
interval	Interval
line	Tipus línia
active_service	Servei actiu
data_activated	Data activació
msidsn	Línia
telecom_company	Operador donant

Also, create new contract lines getting the information from the current lines of the old contract and set the start date to the start_period_date.