Fix purging pre release packages & add missing packages to bom

[jdaugherty]

No description provided.

[jdaugherty]

Ensures the events projects are now in the bom:

  <dependency>
    <groupId>org.grails</groupId>
    <artifactId>grails-events-compat</artifactId>
    <version>${grails-async.version}</version>
  </dependency>
  <dependency>
    <groupId>org.grails</groupId>
    <artifactId>grails-events-gpars</artifactId>
    <version>${grails-async.version}</version>
  </dependency>
  <dependency>
    <groupId>org.grails</groupId>
    <artifactId>grails-events-rxjava</artifactId>
    <version>${grails-async.version}</version>
  </dependency>
  <dependency>
    <groupId>org.grails</groupId>
    <artifactId>grails-events-rxjava2</artifactId>
    <version>${grails-async.version}</version>
  </dependency>
  <dependency>
    <groupId>org.grails</groupId>
    <artifactId>grails-events-spring</artifactId>
    <version>${grails-async.version}</version>
  </dependency>
  <dependency>
    <groupId>org.grails</groupId>
    <artifactId>grails-events-transform</artifactId>
    <version>${grails-async.version}</version>
  </dependency>