bundle lark-parser with Charliecloud

Charliecloud currently needs users to manually install lark-parser in order to use ch-image which could be a barrier for people. If we shipped a version of lark-parser with Charliecloud we could default immediately to using unprivileged image building with ch-image instead of defaulting to docker. A lot of our builder scripts default to docker if you don't specify something else. With some changes users could not have to install docker or another builder.

Options

1. Install lark-parser using setup.py from either a git submodule or tar release
2. Include lark-parser as a submodule and just change charliecloud module paths to look for it internally instead of in the system python
3. Make ch-image a python module and let pip handle the requirements of requests and lark-parser
4. ??

There could be distribution options I have not considered or learned of we could explore. lark-parser has an MIT license so we should be able to ship it with Charliecloud. This could help clear up confusion for users between the lark module and lark-parser module. This could simplify the install process for users.