Change text phrase tagging. (maybe)

[simjanos-dev]

Currently texts gets tagged with phrases when they get imported, or when a new phrase is saved.

Tagging text with phrases could happen when the user opens a text in the text reader instead. It would remove the ability to search phrases on the vocabulary page by book and chapters. But it would also remove performance issues that increase with every imported text.

Not sure which system is better, they will have to be tested.