Slc.zopescript

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- ZCML namespace cleanup.
[thet]

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- Added InstanceScript class for use with `instance run`.
[reinhardt]

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- Improve log handling:

* only log errors during startup
* log INFO to stdout
* log ERROR to stderr
* log to instance's event.log too

This makes it possible to only escalate errors in cronjobs, send
normal logging to /dev/null and protocol what has been done in
the instance.log

[frisi]

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- traverse to context as run_as user [reinhardt]
- Allow selecting a portal by id [reinhardt]

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- better manifest [reinhardt]

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- Allow passing a context_path [reinhardt]
- Updated README [reinhardt]