site create: rename --site_id= to --network_id=
site create: alias --site_id= to --network_id=
Merge pull request #523 from wp-cli/blog-site-network

Rename `blog` to `site` and `site-meta` to `network`
A basic test for converting an install to multisite.
behat: try running the install-network command again
rename _hook() to _action()
help: move duplicated function_exists() check to __invoke()
introduce WP_CLI::log()

WP_CLI::line() is for spitting something to STDOUT.

WP_CLI::log() is for sending a message to the logger, which could do
various things with it.

closes #465
convert from WP_CLI::line() to WP_CLI::log() where appropriate
remove redundant arg check in Theme_Command::parse_name()

it's already handled by the synopsis parser
Merge pull request #471 from wp-cli/psr-3

Switch from WP_CLI::line() to WP_CLI::log() where appropriate
move command instance creation to a separate class

Keep the disabled_commands logic inside the WP_CLI class; show an
explicit error, instead of pretending the command doesn't exist.
move setting $_SERVER['DOCUMENT_ROOT'] to set_wp_root() method

It was first defined in 390e7dbbabee7398527c3a1552e849f5c87053aa and
then sort of drifted away from where paths are handled.
implement '@when' docblock tag

Works on both commands and subcommands.
calculate path for early commands only once
fix network-meta man page. see #529
show error on invalid json. closes #531
Merge pull request #453 from wp-cli/doctag-when

Command phpdoc or other flag to allow third-party commands to run before WordPress is present
add optional 'before_invoke' parameter to WP_CLI::add_command()

this avoids repeating the command name and makes it clearer when the
callback is fired
Support Subdomains