Support for mulitple schemas in one folder

Using the schemas parameter you can filter out on a subset of schemas.

Example:
--schemas=schema1,schema2

Note:
Possible naming collisions are not properly taken care of for now and are to be avoided cross schema for the ones it is generating for

Support custom column type

Support specifying a custom type for a column by using Go struct tag syntax in
comments:

COMMENT ON COLUMN schema.table.column IS 'go_type:"github.com/package/path:ColumnType"';

Make `database` flag work (e.g. historic, app)

Merge pull request #8 from cresta/schema-historic

Fix smallgen to only generate model / dao with flag `database` only

v0.9.30-cresta-fix-4: [plat-908] Add default to generated model

Add default to generated model regardless it's a function or not

v0.9.30-cresta-fix-3: Merge pull request #3 from xingjianan/patch-1

Use sql.NullTime instead of time.Time when the column is empty

v0.9.30-cresta-fix-2

Merge pull request #2 from cresta/fix-postgres-table-schema

Update packaged templates

v0.9.30-cresta-fix-1

Fix generated struct name.

Bump version number so that it can be retrieved with @latest tag

fix 1: Support postgres table schema

v0.9.29-cresta-fix-1

UPdate the package name, so that we can use go install to install it