support for google cloud storage module
gc_storage rewrite commit 1
gc_storage rewrite commit 2
adding Google Compute Engine modules and inventory plugin
custom user-agent header
address a few review comments
update defaults and help for 'name' and 'instance_names'
Merge pull request #4553 from mmoya/features

Do key validation only when key is provided
Fix typo
Merge pull request #4559 from greenalto/fix_typo

Fix typo
Merge pull request #4395 from erjohnso/devel

adding Google Compute Engine modules and inventory plugin
Merge pull request #4333 from bennojoy/gcs

support for google cloud storage module
Various standardization to the proposed gce_storage module to bring things in line with updates to the S3 module.
Some typo fixes.

Further testing required.
Improve change detection in mysql_variables

mysql_variables bindly executes a SET var = value query even when
the variable already has the requested value.

With this patch the query is executed only if the current value is
different to the requested one.