Unify command interfaces to use the same flags

[willosborne]

Feature Request

Description of Problem:

Currently the different commands have some inconsistencies in their usage that may be confusing to users.
For example, the validate command uses -m or --metaSchemasLocation to set a directory of schemas to load, whereas generate uses -s or --schemaDirectory.

These should be made consistent.

Potential Solutions:

Use --schemaDirectory in the case given. But we should also consider other parameters.
Documentation should be updated, too.

[willosborne]

We should also make the -m flag on validate behave the same as -s on generate - it should recursively traverse the directory and load all schemas. Currently it only looks at the top level folder.