change type of vin to numeric in issueasset response.

[AkioNak]

vin may always represents as numeric in rcp wallet(asset) command response.
but current implementation is following.

rpc command	response	help text
issueasset	string	(not descripted)
reissueasset	numeric	(not descripted)
listissuances	numeric	numeric

[instagibbs]

utACK

[jtimon]

Perhaps s/input number/input position/ ?
Perhaps also s/vin/nIn/ or s/vin/in_pos/ or something?

utACK

[instagibbs]

I think vin follows the established standard ie vout in createraw etc.

[instagibbs]

please squash and I'll merge

[AkioNak]

@instagibbs done.