Support for custom list of adapters/plugins in build

Add support for comma/space separated list of adapters or plugins
as cli parametrs.

Eg:

To build only idb adapter, use

    grunt --plugins=mapreduce

or to build only idb and http adapter, use

    grunt --adapters='idb http'

Signed-off-by: Rohan Jain <crodjer@gmail.com>