Add input selection implementation
Move input selection code from waddrmgr to votingpools
Rename badly named function
Make InputSelection a votingpool method
Remove redundant part of credit name
Add comments
Generalize InputSelection to cover more than one series
Add support for nested or composite errors
Make assumption explicit and error out if violated
Move functions to votingpool struct and make them private
Fix getEligibleInputs so it iterates over only well defined range of a series

Introduced the SeriesRange struct to defined a range on a series
Remove unused/ill-defined Distance metric
Add SeriesRange test
Rename SeriesRange to AddressRange as it more accurately reflects what it is
Add a test for getEligibleInputs looking for inputs in a slice of ranges
Make tests work again after rebase
Fix weird comment
Reintroduce comments that went missing in rebase conflict resoltion
Rename function
Delete obsolete test