Voting Pools - Deposit side
Test helpers to create arbitrary unspent outputs
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