Additional Kotlin extensions

ObjectBox already provides some minimal Kotlin extensions:

// Regular
val box: Box<DataClassEntity> = store.boxFor(DataClassEntity::class.java)

// With extension
val box: Box<DataClassEntity> = store.boxFor()

// Regular
val query = box.query().`in`(property, array).build()

// With extension
val query = box.query().inValues(property, array).build()

This issue is to track what other Kotlin extensions may be added.

Some ground rules:

• should leverage features unique to Kotlin
• should not just be a shorter version of an existing method
• should not optimize fur just a single use case

Things to look out for:

• default args for methods
• builder pattern
• making util methods discoverable from the type they operate on
• destructuring

-ut