[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
[TASK] Remove empty sheets in built config but do not remove them from original

Fixes: #260
[TASK] Reorder test assertions to support check on empty Container
Merge pull request #262 from NamelessCoder/cleansheet

[TASK] Remove empty sheets in built config but do not remove them from original
[TASK] Remove legacy scripts used to convert from ancient FED sites
Merge pull request #264 from NamelessCoder/removescripts

[TASK] Remove legacy scripts used to convert from ancient FED sites
Merge pull request #256 from NamelessCoder/handllle

[TASK] LLL-related adjustments
[TASK] ContentManipulator refactoring
[TASK] Remove unexecuted early return
[BUGFIX] Use raw array assignments for hook subscribers
[TASK] Error tolerance when reading Grid from non existing template
[TASK] Refactor content detection methods into ContentManipulator
[TASK] Extend tests to cover new code
[DOC] Adjust a comment's indentation
[TASK] Refactor another record manipulation method to ContentManipulator
[TASK] Cleanup of paste behavior