renaming `vocab` to `lemma`

name of table `pw_vocab_ru` changed to `pw_lemma_ru` (field `word` to
`lemma`), added field `origin` indicating from where this lemma was
gotten (0 - the page exists in wiktionary, 1 - from related words, 2-
from meaning)
PhpMorphy

1. PhpMorphy library added
2. Example for lemmatising of words from meanings of given word