Backtrader-paperswithbacktest

- Fixes 31 - Packaging issue under Python 3.x introduced in 1.1.17.88

- 29 extend commissions to support additional schemes
- 27 convert iterable in pandas datasource to list before checking len
- Packaging reordering to suppor introduction of dependencies

- Correct missing super in start some Data Feeds. Closes 27

- DivByZero function included to perform division without triggering
exceptions
- SessionFiller completed as data filter
- Corrections to WriterStringIO
- Final renaming of data filter API
- Reset of operators to stage1 to be able to run over same data again withoug
re-init
- Update data-replay/resample samples to use new filter API
- Rework of testcaes to use new filter API and run all combinations of
runonce/preload

- Comminfo passed down to trades for multitrade profit and loss calculation
for issue 226
- Addition of filters/processors (naming not final) to data sources
- (Re)Implementation of Resampling/Replaying as Processors - Old
Implementation still available
- Changed X axis formatting for Weeks/Months/Years
- DataFilter/DataFiller implemented as DataSources and also as
Filters/Processors
- DataFilter/DataFiller sample
- Time management improvement to address precision issues when isolating time
from coded datetime with new functions in LineBuffer

- Further refactoring of resampling (keeping previous parameter names
compatible) killing corner case for last bar still having the sub-bar
timestamp - Close 25
- Added sessionstart parameter to DataBase to complement sessionend
- Some module import refactoring to refer to main module
- Added DataFilter class
- Close 24 by enabling writer to handle Analyzer dictionaries which carry
non-string as keys
- Correct/enhance some of the samples