Add sample output of running billsplit with given sample bill.
Use billsplit as module and call from bill.py.

This allows having multiple bills with different names.
Whole functionality is moved to method billsplit() in billsplit module.
Use coversion rate, if present in bill.
Introduce automatic conversion from other currencies to EUR.
Currencies are obtained from ECB.

Bill dicts are extended by
    'date':     "%Y-%M-%d" used for conversion
    'currency': ISO 4217 Currency Code as string

Patch by Philipp Tölle including fix by me.

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Original patch message:

Updated bill format, now the following form is required:

{
    'name':    <String> #String
    'lender':  <defined Lender> #String
    'debtors': <defined debtors> #array
    'amount':  <amount of bill>, #float or float expression, in native bill's currency
    'comment': <more information>, #String
    'date':    <date of bill>, #String format: "%Y-%M-%d" Example: "2013-09-05" this date is used for reference conversion rate
    'currency' : <Native currency of bill> #String containing an ISO 4217 Currency Code
}

modified bill file to comply with new format, all calculation, that were done in conversion attribute are move to amount.

PLEASE CHECK

Conversion rate is retrieved vom ECB.

backup of berlin bill.py

TODO get conversion rate only once, not for every bill from ECB
TODO Error handling for conversion rate parser, conversion rate retrieval
TODO complete Bill format checker