common/bloom_filter: unit tests

Fun facts:

- fpp = false positive probability
- fpp is a function of insert count only
- at .1% fpp, we pay about 2 bytes per insert
- at 1-2% fpp, we pay about 1 byte per insert
- at 15% fpp, we pay about .5 bytes per insert

Signed-off-by: Sage Weil <sage@inktank.com>
common/bloom_filter: test behavior of sequences of bloom filters

Signed-off-by: Sage Weil <sage@inktank.com>
common/bloom_filter: fix whitespace

Signed-off-by: Sage Weil <sage@inktank.com>
COPYING: make note of common/bloom_filer.hpp (boost) license

Signed-off-by: Sage Weil <sage@inktank.com>
common/bloom_filter: insert/contains methods for uint32_t

This will let us pass in an hobject_t::hash directly (for example) without
rehashing a string.

Signed-off-by: Sage Weil <sage@inktank.com>
common/bloom_filter: disable sequential tests

These are slow and are not useful.

Signed-off-by: Sage Weil <sage@inktank.com>
common/bloom_filter: test binning fpp behavior

Signed-off-by: Sage Weil <sage@inktank.com>