v1.0.2: presets + random order + populate again + truncation

- Presets fully complete - asset/image paths are relative to the
preset's JSON and can also refer to upper level folders using '../'
(see 'short.json' in contacts)

- Data order can be randomized using the checkbox - the plugin makes
sure that the same data row is not chosen consecutively and that all
data rows have been chosen before starting to repeat

- 'Populate with JSON' now also has a UI panel with configurable options

- 'Populate Again' populates the selection with the last used
preset/JSON and options configuration

- Truncation consists of two parts: trimming overflowing text and
inserting the ellipsis (both options can be configured independently)

NOTE: Truncation only applies to 'fixed' width text layers (see updated
demo.sketch). Using a character count has proven to be unreliable since
character width varies considerably, e.g. 'w' compared to 'i'.

v1.0.1: preparation for new features + introduced presets

NOTE: The original JSON method is still available through the 'Populate
with JSON' command

- Added new alert style UI for selecting presets and setting options
(not fully complete yet)

- It is possible to populate layers using presets using the 'Populate
with Preset' command

- The 'randomize data order' option is not implemented yet

- The truncation option should be added to the panel

- Presets can be revealed using the 'Reveal Presets' command

v1.0.0

Initial commit