Extend base value object
Implemented Solr facet handling

Only for one single facet yet
Handle facet return values correctly
CS
Implemented ContentFieldValidationException
Added: getFieldDefinitionById() abstract declaration
Fixed: phpdoc typo
Removed extraneous empty line
Fixed: phpdoc hinting and typo
Fixed few phpdoc typos, removed resolved todo
Added: getValidatorService() declaration
Removed: implemntation method abstract declaration
Refactored FieldType validators and settings
Fixed fixture names
Implemented: Section facet builder visitor
Implemented: User facet builder visitor
Implemented: DateMetadata range criterion visitors

Those class constants in the criterion API and the resulting
switch-cases are aweful to handle.
Implemented: Status criterion visitor
Tested: Field and FullText searches
Fixed: Typos referring to Core namespace in docs.