Add max lengths to database string columns if desired

[hhyyrylainen]

Looks like the string length attribute ([StringLength(255)]) can be used to restrict how long text can be put in a database column. With PostgreSQL this doesn't have a performance impact, just a data validness check. So if desired this can be done. Note that if done then the following warning should be re-enabled:

	<s:String x:Key="/Default/CodeInspection/Highlighting/InspectionSeverities/=EntityFramework_002EModelValidation_002EUnlimitedStringLength/@EntryIndexedValue">SUGGESTION</s:String>