Redesigned Restriction class

testing needed still
test cases for Table.java

Changes to Table.java:
----------------------
- static list of Tables changed to Hashtable
- un-/seatPerson changed from package-private to public
- added private copy-constructor
static storage method changed to hashtable implementation

Changes to person.java:
----------------------
- static list of people changed to Hashtable
- added private copy-constructor
changed method of getting objects is now O(1).

getPersonByName and getTableByName now uses the hashtable implemented by
both Person and Table