Command check

[sveetch]

Is your feature request related to a problem? Please describe.

Currently, the diskette configuration settings are only validated when dumping or loading.

Describe the solution you'd like

Current behavior is working but it could be more helpful to diagnostic invalid configuration without to dump or load anything.

New command diskette_check would be able to:

• Inspect application definitions to find invalid configuration;
• Inspect storage definitions to find invalid storage paths;
• Hint about storage sizes that would be dumped (this can help when writing storage exclude patterns);

This will never try to hint about data size since it could be stressful for database to count on everything.

[sveetch]

Adding a new command for this was impractical and not very DRY to implement.

So instead, the existing command dump and load will include a new option --check to perform a dry-run.

Since these command already perform validations, we can use the same routine but without writing, querying or loading anything.

The check option for dump has been implemented and tested in v0.3.3-pre.1