[java] vector template cleanup

[asfimport]

Reduce the checks for a specific type in templates.
Remove old code related to removed types.

Reporter: Julien Le Dem / @julienledem
Assignee: Julien Le Dem / @julienledem

_{Note: This issue was originally created as ARROW-1049. Please see the migration documentation for further details.}

[asfimport]

Julien Le Dem / @julienledem:
Issue resolved by pull request 703
#703