* Fix schema validator
It should use the passed schema.
* Add required attributes to keymap schema
* Rework subcommands to validate the JSON keymaps
The 'compile', 'flash' and 'json2c' subcommands were reworked to add
JSON keymap validation so error is reported for non-JSON and
non-compliant-JSON inputs.
* Fix required fields in keymap schema
* Add tests
* Fix compiling keymaps directly from keymap directory
* Schema should not require version for now.
fbfd5312b9