suppress model_class field in json output.
format json according to data type. also fix a bug that it only escape " in string.

null, true, and false are respected.
escape string according to json.org.
Date/Timestamp object is converted to iso8601 UTC format.
cleanup.
Fixes schema issue(#182)

Moving away from system prop to get the schema name.
usage: if schema is used you'll have to use @Table annotation
instead of @Table("tablename") use @Table("schemaname.tablename)
Merge pull request #195 from huochunpeng/json_with_types

generate JSON respecting data type
Merge pull request #196 from barunsthakur/schema_issue_fix

Fixes schema issue(#182)
do not treat db as inited, if exception happened during Registry.init()
Merge remote-tracking branch 'origin/master'

Conflicts:
	activejdbc/src/main/java/org/javalite/activejdbc/Registry.java
remove id attr before setting reference, otherwise concurrent modification exception, if the code should be 100% correct - use double check locking with volatile, now few instances may be created