* remove conditionl require in runner
add tasks module to load all tasks, throw if task does not exist
* change task signatures and action handlers
- tasks get plugin, run, and an options object
- action handler controls what goes into each task
- taskRunner wrapper moves the command object to the first argument
* change test command signature
allow files to be passed in, and pass all options to test:server and test:browser
* simplify the task runner
* fix typo in unknownOptions
* expose the task runner as the module's main
this way tasks can be run programatically without going through a cli parser
* add tests for task runner
* remove file passing for testAll
* add serverTestPaths to the plugin config
useful for overriding the value via a config file
* [config] plugin.serverTestPaths -> plugin.serverTestPatterns
Original commit: elastic/kibana-plugin-helpers@82af4df64e
0d621e778a