Import custom fields in templates from Quick Subtasks for Jira

[Stefan Glase]

As an administrator I want to import templates that are using custom fields, too, and not loose this information during the import. This feature relies on #91 to be implemented first. After that we can import custom fields from Quick Subtasks for Jira, too.

Format of imported data

- Test / cfield:"somenumber:3.5"
- Test / cfield:"cf1:@inherit" cfield:"cf2:@inherit"
- subtask / cfield:"cfieldname:this is a list{n}* one{n}* two{n}* three{n}"

Tasks

• import cfield using syntax implemented in #91
• update known limitations in documentation for Import