gen: support boolean path arguments
gen: support boolean path arguments

Support a method argument with location "path" and type "boolean".

Change-Id: Ie7d743341990296a4de43d1584d121b97030c865
Reviewed-on: https://code-review.googlesource.com/23370
Reviewed-by: Ross Light <dfccc06f14414bff5a59be7fc90abf4404b47fc8@google.com>

google/google-api-go-client,googleapis/google-api-go-client,google/google-api-go-client,googleapis/google-api-go-client