v1.3.1

Deploy apollo-gradle-plugin to plugins.gradle.org (#1932)
Fix licenses overwriting the main url (#1939)
Remove the 1.3.0 warning (#1942)
Remove bintray plugin and upload marker to bintray (#1933)
Allow to override operationIdGenerator from onCompilationUnits (#1949)
Generate default value for __typename field (#1944)
Rename all singular CompilationUnit references to singular (#1951)
Add support for auto persisted subscriptions (#1943)
Field with inline fragment forced to be optional (#1960)
Generate CustomType enum constants ordered by name (#1959)
Avoid field names clash (#1958)
Sanitize yield keyword in Kotlin (#1971)
Use KotlinProjectExtension instead of the reflection magic to get a kotlin sourceDirectorySet (#1978)
Fix Object type name collision (#1979)
Fix compile task naming (#1982)