DCAPI: handle failure better on include and for sketch_template, use zmain.cf
sketch_template: use zmain.cf
sketch_template: zmain.cf is not an interface
DCAPI: add activation hash to activations
howto/dc_api.md: update to mention activation hash
DCAPI: stringify special run environment keys (activated, verbose, test, qa)
Removed stdlib and cfengine version dependency.

CFEngine::stdlib no longer exists in 3.6, instead the standard stdlib is
assumed to be available. Also remove check for CFEngine version, may get
readded in the future.
Update include block for 3.6

Include the standard.inc file instead of the inlined code that was used
before. Also updated some of the messages to fit the new structure.
Fixed typo
Fix empty result from get_all_sketches

When no results are found, return an empty hash instead of an undef
value.
Prevent variable expansion before regex eval

Use the variable without expansion in the eval, so that special
characters in the variable value do not cause errors when parsing the
regex.
Skeleton for new `sketchify` command

Renamed old command to sketchify_old during transition, added skeleton
for new sketchify command, which will be able to both create new
sketches and update existing ones.
Added .DS_Store
Almost-complete reimplementation of sketchify

Reimplementation and restructuring. Still missing:

- Check and add of runenv and metadata parameters to sketches
- Writing out the finished sketch
- Sketch-edit mode.