jsonconfig: Int64 support

Change-Id: I933e5f86d0f5a55402ab9218fba8ffbfee8efa26
Start of 'proxycache' blobserver type.

Change-Id: I8702c1d02203090899eee6c0a555f6fc1dba4e7e
Rewrite Picasa importer for the new Importer API

Reorganizes common OAuth2 things into importer/oa2_importers.go

Change-Id: I0789f4732412aa559078ec2c6b6797925ab8cd05