Added configuration options for:
* verification: FULL, CHECKPOINT, MINIMAL, NONE - specifying which part of the blocks should be verified (signature verification)
* validation: FULL, CHECKPOINT, MINIMAL, NONE - specifying depth to which MerkleTrie hashing should set in - note that the first time you switch on validation libcoin will segfault, next time startup will be slow as it takes time to rebuild the merkletrie in memory
* persistence: FULL, CHECKPOINT, MINIMAL, NONE - similar to pruning, specifies the amount of blocks to keep stored.
* searchable: (bool) keep an index or not for the scripts enabling fast address lookup (always true for coin explorer)