Deleting Author, Contributor and Modifier classes in favour of Person

Deleting Author, Contributor and Modifier classes in favour of Person
Fixed uses of Author, Contributor and Modifier classes
Remove Tag classes other than Common

Remove Tag classes other than Common
Merge remote-tracking branch 'origin/2.0.0-alpha' into
java-refactor-common-entities

Conflicts:
	sdk/com.ibm.sbt.core/src/main/java/com/ibm/sbt/services/client/connections/blogs/BlogService.java
Merge pull request #1472 from CarlosManias/java-refactor-common-entities

Java refactor common entities