Add dpsRemove functions that do not lock the store

[brandtol]

To remove keys from the store, the dpsRemove/dpsRemoveTTL functions lock the store before
removing the key. This impacts performance. One possible improvement would be to provide
new unsafe versions of the calls, which do not lock the store. Eg.
dpsRemoveFast() or dpsRemoveUnsafe() or similar.

[nysenthil]

Hi Oliver,
We can do the same way how it is already done for dpsPut, dpsPutSafe, dpsGet and dpsGetSafe.

We will keep the existing dpsRemove method and change it to not perform store existence check and other goodies which will make it perform slightly faster. We will create a new method called dpsRemoveSafe which will do the safety checks such as checking for store existence, locking the store for brief period etc.

[anouri]

no demand for long time