add support for withValidatorMethod
Guava optional support: WIP
Guava optional support: Functional but not yet using Enum on GPB annotation
Use OptionalSupport enum (but with a nasty hack in implementation)
Optional class should be configurable to support Guava and Java 8
Improve javadoc of GeneratePojoBuilder
Allow a custom method name prefix
Support validator class
Merge branch 'tsouza-master'

Conflicts:
	src/main/java/net/karneim/pojobuilder/GeneratePojoBuilder.java
	src/main/java/net/karneim/pojobuilder/analysis/Directives.java
	src/main/java/net/karneim/pojobuilder/analysis/JavaModelAnalyzer.java
	src/main/java/net/karneim/pojobuilder/model/BuilderM.java
	src/main/java/net/karneim/pojobuilder/sourcegen/BuilderSourceGenerator.java
Refactor custom method name prefix
Merge branch 'drekbour-optional-guava'

Conflicts:
	src/main/java/net/karneim/pojobuilder/GeneratePojoBuilder.java
	src/main/java/net/karneim/pojobuilder/analysis/Directives.java
	src/main/java/net/karneim/pojobuilder/analysis/JavaModelAnalyzer.java
	src/main/java/net/karneim/pojobuilder/model/BuilderM.java
	src/main/java/net/karneim/pojobuilder/model/PropertyM.java
	src/main/java/net/karneim/pojobuilder/sourcegen/BuilderSourceGenerator.java
Add unit test for bad validator class
Assert that validator mus have a public no-arg constructor