Remove dead transaction replacement code

This dead code can be resurrected from git history if
transaction replacement is ever implemented. Keeping
dead code in the source is a bad idea, because it implies
it was tested and worked at some point, which is not true.
Refactor: move GetValueIn(tx) to tx.GetValueIn()

GetValueIn makes more sense as a CTransaction member.
Add verbose boolean to getrawmempool

Also changes mempool to store CTxMemPoolEntries
to keep track of when they enter/exit the pool.
Merge pull request #3239 from gavinandresen/mempool_verbose

Add verbose flag to getrawmempool