[TASK] Move LLL handling to base Form Component and Interface

This enables the use of LLL-affecting properties on every Form Component type and ensures that if set on the parent container BEFORE a child is created from this container, these values will be transferred to the child. This makes it possible to change the location of the LLL file on-the-fly, for example using one LLL file per sheet (which may help if your form is huge).
[TASK] Support separator and adjust LLL value resolving
[TASK] Adjust and extend unit tests for newly added code
[TASK] Auto-add field to TCA as type "flex" if listType provided
[TASK] Extend unit tests to cover newly added code
Merge pull request #256 from NamelessCoder/handllle

[TASK] LLL-related adjustments