Docassemble

Added
- The `logo` option of `set_title()` and `metadata`.
Changed
- The `all_variables()` and `variables_as_json()` functions now
contain a limitation on nesting depth. The limit is hard-coded at
6 levels, after which values will be "null." This is to prevent
exceptions being triggered by circular references.
- Setting Google Drive Synchronization folder to "Do not link" will
now erase the connection between the OAuth app and the user.
- When populating PDF checkboxes, passing `None` to the checkbox or to
the `yesno()` or `noyes()` functions will result in the box not
being checked.
- Apache web server variables are now reset after a restart (e.g.,
after the Configuration is changed.
- When pulling the contents of a **docassemble** extension package
into the Playground, it will now remember the GitHub URL or PyPI
package name so that when you go to Pull again, you will not need to
retype. This works even if you have not enabled GitHub integration.
Fixed
- PDF checkbox inconsistencies.
- Git pull into Playground packages without integration generated an
error message.
- When datatype is object and variable existed, it would try to reduce
the object to text in order to see if it should be highlighted as a
pre-selected default value.

Added
- Option for changing the UID and GID of www-data within the Docker
container, so that `/usr/share/docassemble/files` can be mounted as
a Docker volume and the Playground files can be edited.
Changed
- Multiple choice questions in `fields` will set boolean `True` or
`False` if those are the only options.
- Additional headers are set to enable cross-site resource sharing
if the CROSSSITEDOMAIN variable is set.
- Apache configuration files in Docker are configured differently;
existing site configuration files will not be overwritten and
configuration options are now implemented as Apache variables.
- `DAList` objects now work with the `+` operator; a regular list can
be added to a `DAList` but not the other way around.
Fixed
- The `uncheck others` feature triggered an error if it was not the
last field.

Changed
- Going to "/exit" will now log out the user, if the user is logged
in.
- When using `&json=1` for JSON responses, the `interface()` function
will return `'json'`.
Added
- Action for `logout`, which works like `exit` but also logs the user out.
Fixed
- Default values in object choices.

Fixed
- JavaScript issue with buttons.
- Problem with Playground interviews not being decrypted.

Fixed
- JSON conversion problem when using `/interviews?json=1`.

Fixed
- Bug in 0.1.94 regarding detection of variable names.