OFStateManager: remove support for expiring flows in Forwarding

None of our switches do this, and a switch that did would have to reimplement a
bunch of expiration.c to ratelimit the flow-removed messages and send flow-idle
notifications when necessary.

Once we're fully transitioned to the new flowtable APIs, ind_core_flow_removed
would be the only remaining user of the flow-id hashtable.
Merge into master from pull request #156:
OFStateManager: remove support for expiring flows in Forwarding (https://github.com/floodlight/indigo/pull/156)
OFStateManager: remove flow-id hashtable

This was unused except by the unit test.
Merge into master from pull request #169:
OFStateManager: remove flow-id hashtable (https://github.com/floodlight/indigo/pull/169)
OFStateManager: remove calls to old flowtable API

All flowtables must now be registered with indigo_core_table_register.
OFStateManager: remove weak symbols for old flowtable APIs
indigo: remove deprecated flowtable APIs

These have been replaced by indigo_core_table_register.
OFStateManager: remove uses of deprecated group APIs
OFStateManager: remove weak symbols for deprecated group APIs
indigo: remove deprecated group APIs

These have been replaced by indigo_core_group_table_register.
Merge into master from pull request #170:
Remove deprecated APIs (https://github.com/floodlight/indigo/pull/170)
OFStateManager: remove unused functions from utest
OFStateManager: remove "disconnected mode"

While the disconnected mode could be configured, it didn't actually have any
effect.
OFStateManager: remove max_flowtable_entries

This option had no effect.
Merge into master from pull request #171:
Remove more dead code from OFStateManager (https://github.com/floodlight/indigo/pull/171)
OFStateManager: create a struct for cookie buckets

More fields will be added to this struct in the future.
OFStateManager: remove unused flow_id_hash_entry field
OFStateManager: update comments for ft_entry_t

Also moved and resized fields for better packing.
OFStateManager: remove unused query modes
OFStateManager: remove support for overlap checking

No sane controller would ever set this flag. It requires a linear scan through
the flowtable.