Allow primary keys to be any type, and test it.

Allow primary keys to be any type, and test it.

        * src/main/java/org/glom/web/shared/TypedDataItem.java:
Add overrides for the other set*() methods, to set the type.
        Added getValue() which returns a generic Object.
* src/main/java/org/glom/web/server/SqlUtils.java:
buildSimpleWhereExpression(): Use TypedDataItem.getValue() instead of
getNumber().
        * src/test/java/org/glom/web/server/SelfHostExampleNonNumericPrimaryKeysTest.java:
Added this test, which is much like SelfHostExampleTest, but which uses this
test file, take from Glom:
        * src/test/resources/org/glom/web/server/test_example_music_collection_text_pk_fields.glom:
which has all the primary keys changes to text instead of numbers.

However, parts of the UI code still assume that primary keys are numbers.