change currency three-letter-code to DOGE

also change length of currency amounts in UI

(cherry picked from commit inutoshi/inutoshi@8dcef8791a02327c8061235df7a77e2da6b59ee2)
Merge pull request #364 from rnicoll/1.7-dev

Rework documentation and English and French translations to refer to Dogecoin
Merge pull request #363 from leofidus/1.7-currencyname

1.7: change currency three-letter-code to DOGE
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
Updated code references to bitcoin, with dogecoin.
Corrected name of generated binaries to dogecoind and dogecoin-qt.