Also match {} as type array (non-string) and allow trailing whitespace

[BoostCookie]

Fixes #544

This commit also passes environment values directly (instead of as string) to the settings.py if the value starts with { and ends with }. Trailing whitespace is also allowed.

This allows correctly parsing settings such as

services:
  ...
  zulip:
    ...
    environment:
      ...
      SETTING_SOCIAL_AUTH_SAML_TECHNICAL_CONTACT: |
        {
            "givenName": "Technical team",
            "emailAddress": ZULIP_ADMINISTRATOR,
        }
      DB_HOST: "database"
      ...

which the entrypoint.sh sees as the string

'{
	"givenName": "Technical team",
	"emailAddress": ZULIP_ADMINISTRATOR,
}
'

(Notice the trailing whitespace.)

Without this modification the resulting settings.py looks like

SOCIAL_AUTH_SAML_TECHNICAL_CONTACT = '{
    "givenName": "Technical team",
    "emailAddress": ZULIP_ADMINISTRATOR,
}
'

With this modification it looks like

SOCIAL_AUTH_SAML_TECHNICAL_CONTACT = {
	"givenName": "Technical team",
	"emailAddress": ZULIP_ADMINISTRATOR,
}