Move sql store code into store/sqlstore package (#7502)

* move sql store code into store/sqlstore package

* move non-sql constants back up to store

* fix api test

* derp

store/constants.go

@@ -0,0 +1,15 @@
+package store
+
+const (
+	MISSING_CHANNEL_ERROR        = "store.sql_channel.get_by_name.missing.app_error"
+	MISSING_CHANNEL_MEMBER_ERROR = "store.sql_channel.get_member.missing.app_error"
+	CHANNEL_EXISTS_ERROR         = "store.sql_channel.save_channel.exists.app_error"
+
+	MISSING_ACCOUNT_ERROR      = "store.sql_user.missing_account.const"
+	MISSING_AUTH_ACCOUNT_ERROR = "store.sql_user.get_by_auth.missing_account.app_error"
+
+	USER_SEARCH_OPTION_NAMES_ONLY              = "names_only"
+	USER_SEARCH_OPTION_NAMES_ONLY_NO_FULL_NAME = "names_only_no_full_name"
+	USER_SEARCH_OPTION_ALL_NO_FULL_NAME        = "all_no_full_name"
+	USER_SEARCH_OPTION_ALLOW_INACTIVE          = "allow_inactive"
+)