Fix WP-CLI option output and more

[cssjoe]

• Fixed the WP-CLI option output to escape properly.
• Added a new "json" type for the "option get" and "option set" that outputs valid JSON.
• Applied PHPCS WPCS and formatting.
• Added "w3tc" as a WP-CLI command alias.

Fixes #31

Example commands:

wp w3tc export export.json
wp w3tc export export.json --mode=0400
wp w3tc option set test '{"testing": true, "extra": "stuff..."}' --type=json
wp w3tc option get test --type=json

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 272 lines in your changes missing coverage. Please review.

Project coverage is 0.90%. Comparing base (6eaf6cf) to head (bd58f43).

Files	Patch %	Lines
Cli.php	0.00%	260 Missing :warning:
Config.php	0.00%	12 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #916 +/- ## =========================================== - Coverage 0.90% 0.90% -0.01% - Complexity 19158 19166 +8 =========================================== Files 659 659 Lines 96470 96547 +77 =========================================== Hits 871 871 - Misses 95599 95676 +77 ```

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