v0.12.0 implement kotlin-insight-client-sdk

• rename pageFrom to pageIndex and start counting from 0 to be consistent with jira
• DomainModel now uses sealed classes to represent InsightObjectAttributes to clear up when which values are available
• test all default type variants
• unified errors as a sealed class
• added Repository pattern as an interface with example implementations
• remove manual println from tests
• replace Junit assertions with Hamcrest
• Ids are now wrapped
• Use streams instead of bytearray to reduce memory overhead
• create and update now offer a similar interface
• add JavaDoc to insight interfaces