Extract data from practicalplants properties that contain textual data

[petteripitkanen]

Some practicalplants properties contain free-form text that are not directly useful from an algorithmic point of view, but from some of these it might be possible to extract useful sets of values.

There is already #92 for defining and extracting a set of values that describe geographical areas where a plant grows.

These properties are highly used, see this comment and the following thread for a preliminary analysis:

• habitat
• PFAF cultivation notes
• PFAF propagation notes
• PFAF material use notes
• PFAF toxicity notes
• PFAF medicinal use notes
• PFAF edible use notes

Then there might also be some less used properties (see #74) that contain textual data.