BPFTable contained all of the logic for multiple table types, which is
incorrect since a bpf table has either hash or array behavior.
Additionally, some methods on the classes aren't valid for some table
types. Create HashTable, Array, ProgArray, and PerfEventArray classes to
contain this behavior.

In future, the new Array class and its children should behave more like
an array than a dict as it currently does.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>