[wip] Pr mapping import

# The bug:
1.use symfony2 doctrine:mapping:import from msyql database to annotation
2.use symfony2 doctrine:schema:update will see a lot of sql update about just import database schema.
3.this PR fix eliminate some of those sql update...

# fix 8 bug:
* column default
* column unsigned
* column type char
* table without auto_increment
* column comment
* column type decimal
* table with simple index
* table with unique index

# wip -> follow rule of contribute to doctrine
* add patch on master
* add test