Changed processing unique constraint name.

Function `_raise_if_duplicate_entry_error()` modified respectively to
new unique constraint name convention.

We found that current constraint name convention allows us create
constraints with duplicate names. It happens if we will add constraints
in different tables with same column names (for example, `name`,
`deleted`). In this case we can not create new constraint due to mysql
limitation (it requires unique constraint name for database)
To solve this issue unique constraint name convention was changed
from "uniq_c1_x_c2_x_c3" to "uniq_t$c1$c2$c3" where `t` it is table name
and columns `c1`, `c2`, `c3` are in UniqueConstraint.

Function `_raise_if_duplicate_entry_error()` parse error from
database and provides us correct column names in error message.
So now we receive correct error message from function.

Change-Id: I4a507deba97c499fcd9738d980e36ca0f9454b71
Fixes: bug 1182054
Merge "Changed processing unique constraint name."