Fix Null Pointer Error

CaseDetail, CaseNote
(/=) avoid null pointer error by possibly invoking DateFormat on null
date
Implement add Suspects, prepare add Convicts

PersonSelection, PersonSelectionServlet
(+) implement generic person selection page. Takes a return address as
parameter and appends a personId that the user selected to the url
(+)Search semantic is as follows: If the user specified a valid id,
return the person with that id. Otherwise search by first and last name.

CaseServlet
(/=)Use final constant for string parameters, etc
(+)Implement add Suspects action

Case.jsp
(/=)remove naked constant string parameter values
(+)buttons to add suspects, convicts when logged in

CaseDatastore, CaseDatastoreInterface, DatastoreInterface
(+) add Suspect, add Convict stub

CaseDatastore
(+) Implement add Suspect, prepare add Convict
Merge branch 'master' of https://github.com/vdemotz/IntroDBProject

Conflicts:
	src/ch/ethz/inf/dbproject/database/CaseDatastore.java
	src/ch/ethz/inf/dbproject/database/DatastoreInterface.java
Merge Branch cleanup