Improve GCE Compute driver docstrings.
Improve GCE Compute driver docstrings.

techhat/libcloud,samuelchong/libcloud,ByteInternet/libcloud,andrewsomething/libcloud,StackPointCloud/libcloud,t-tran/libcloud,vongazman/libcloud,illfelder/libcloud,mistio/libcloud,mistio/libcloud,Scalr/libcloud,andrewsomething/libcloud,techhat/libcloud,vongazman/libcloud,ZuluPro/libcloud,illfelder/libcloud,techhat/libcloud,samuelchong/libcloud,apache/libcloud,t-tran/libcloud,ZuluPro/libcloud,erjohnso/libcloud,ByteInternet/libcloud,andrewsomething/libcloud,samuelchong/libcloud,apache/libcloud,ZuluPro/libcloud,apache/libcloud,Scalr/libcloud,Scalr/libcloud,pquentin/libcloud,pquentin/libcloud,StackPointCloud/libcloud,t-tran/libcloud,vongazman/libcloud,Kami/libcloud,StackPointCloud/libcloud,erjohnso/libcloud,Kami/libcloud,mistio/libcloud,pquentin/libcloud,illfelder/libcloud,ByteInternet/libcloud,Kami/libcloud,erjohnso/libcloud