Update bitcoinunits.cpp

Adding a name for the smallest possible unit. :>
Update bitcoinunits.cpp
Update bitcoinunits.h

Adding Koinu @leofidus :D
add megadoge and kilodoge as selectable units
remove millidoge and microdoge units

Users who have set them as display unit fall back to Doge with this change
Merge pull request #366 from leofidus/1.7-kdoge

1.7 Display Unit changes