support pagination in search assets rpc

[bsushmith]

Is your feature request related to a problem? Please describe.
support pagination in SearchAssets rpc.

[ravisuhag]

@bsushmith why do we need pagination in searchAssets? We should only have limit based on number of search results on?

#196

[bsushmith]

Currently we are revamping our UI, and we would like to use this API and show only a few results in search and let user navigate pages if needed based on the ranking strategy that is employed rather than show 100 or 200 which is the default MaxSize.

[ravisuhag]

Would it make sense to use list API in that case?