Utilize correct db error when the duplicate database is created (apac…

…he#39)

As per http://v2.gorm.io/docs/conventions.html#TableName TableName() suppose to generate static names only (it could not be dynamic). The same source suggests a workaround that I implemented as DynamicCasbinRuleTable along with a scoped DB object for NewAdapterByDBUsePrefix.

As a result of 2. we can remove tablePrefix from global state

Signed-off-by: l1ghtman2k <aibek.zhil@gmail.com>

Update README.md

Merge pull request apache#33 from lucidhq/add-remove-policies

Add support for Casbin AddPolicies and RemovePolicies

Merge pull request apache#25 from riceChuang/master

fix when new multi adapter tableprefix bug

Add other badges.

Merge pull request apache#20 from wumoxi/master

fix:fixed a bug with the specified table prefix

Merge pull request apache#15 from pjediny/go-modules-casbin-v2

Add support for Casbin v2.0.0

Remove policy "p, alice, data, 1, 2, 3, read".