Add root to Tree table and fix some related query

As explained in tree table need a root for sql to work well.
The startup query now insert an element with id = 0

During the cleanup I've decided to get rid of the confusing and mostly
redundant TagsTree table. Only for the mysql database for now, since
sqlite has a different structure and use of the tables

A bug found is that tags query had named parameter :tagID mentioned
multiple times in the query which is forbidden by QT implementation.

TODO:
- DELETE in the tags tree is not managed by triggers anymore, will be
managed by multiple query.
(cherry picked from commit ef9afa84ba358ec335816ed345163de9de884cc4)