Adds yotta start aka yotta run defined by targets (defaulted to native execution).
Adds prePublish, postPublish, postInstall, preGenerate, preBuild and postBuild module-defined scripts (plan to add also preTest, preDebug and preStart scripts)
Fixes #518
Fixes #278
Fixes the use case in #611 (though not the request for arbitrary scripts)
Also some other bugfixes and improvements for the existing test and debug script support.
Fixes #234 (.py scripts can be used as testReporters, and their path is interpreted relative to the root of the module)
yotta startakayotta rundefined by targets (defaulted to native execution).testanddebugscript support.