Add javadoc to Operator and ParserUtils.
Remove old SelectionClause class and associated ones.
Merge branch 'release/0.1.0' of github.com:Stratio/crossdata into release/0.1.0

Conflicts:
	crossdata-core/src/main/java/com/stratio/crossdata/core/structures/SelectionClause.java
	crossdata-core/src/main/java/com/stratio/crossdata/core/structures/SelectionList.java
	crossdata-core/src/main/java/com/stratio/crossdata/core/utils/ParserUtils.java
Merge branch 'release/0.1.0' of github.com:Stratio/crossdata into release/0.1.0