Added ITankContainerBucketable

Interface that says whether buckets should be able to fill and drain an
ITankContainer
TEFactoryInventory not bucketable

(By default. The children of this that actually implement
ITankContainerBucketable will need to override.)
Giving iTCB to the liquid fabs

for testing
iTCB on liquid fabs/gens

for testing
iTCB handling in BFM

now I just need to replace the contents of those utils with something
other than "return false;"
manual tank filling implemented
manual draining of tanks