Wrappers for commit_entry and get_entry

[willemolding]

Quite a lot going on in this PR. I'll make future ones more focused

• Merges app-spec-asm in to this repo under examples
• Updates how strings are deserialized so string concatenation is no longer used. This was causing problems
• Adds a wrapper for commit_entry which is working correctly including returning the hash
• Adds wrapper for get_entry that is successfully able to retrieve the committed data
• Adds ability to decode and print holochain error codes which helps a lot with debug

What it doesn't do yet... consumer of this library, like /examples/appSpec still need to manually serialize/deserialize inputs and outputs`

[Connoropolous]

@willemolding seems there is only one tiny issue, we can create a "follow-up" issue for it, in which the string being returned has an extra 'null' unicode char on the end. See \u{0} where the \u indicates unicode, and the {0} indicates the null char, according to wikipedia (and @ddd-mtl )

See the last characters of these results

This means having to do

let raw_commit_result = raw_commit_result.trim_right_matches(char::from(0));

to cut those characters off.

I think it's fine for now, because the parts we want working are working.