Add a non-strict mode

[setr]

Non-strict will be the default mode new flag --strict In certain cases, we can handle errors and continue anyways. The original error is printed as a warning.

1. If a post is referenced as parent, but does not exist, add an empty post with its name
2. If a dirname is referenced but does not exist, add an empty category with its name
3. If a field exists but shouldn't, warn but drop the value

[setr]

clarity of #19

[setr]

Added --strict mode, with nonstrict as default, and missing parents are now being faked with a new, empty, post.

items 2 & 3 are still incomplete.

[setr]

Moving items 2 & 3 to v0.3, as its a bit invasive, and useful but not that useful.