Add custom_data support to more resources

Previously only available on Accounts, now added for Application,
Directory, Group and Tenant Resources.
Ignore provider data if provider is Stormpath

Provider should be treated as read only when the default Stormpath
provider is used. It should be changable and therefore savable only
for 3rd party providers.
improve cleanup with live tests
remove custom data tests from account
add live tests for custom data

for all resources that have custom_data
Merge pull request #82 from denibertovic/custom_data

Add Custom data to other resources