Add new column in styles to register the id.

We do not want to depend on rowid for the style id.
Fix styles support to use the new styles.id instead of rowid.

We do not want to use rowid as a key as rowid may change when the database
is compressed (vacuum).
Merge branch 'fix-style-table'

* fix-style-table:
  Fix styles support to use the new styles.id instead of rowid.
  Add new column in styles to register the id.