Planetary Candidates Observed by Kepler. V. Planet Sample from Q1?Q12 (36 Months)

The Kepler mission discovered 2842 exoplanet candidates with 2 yr of data. We provide updates to the Kepler planet candidate sample based upon 3 yr (Q1?Q12) of data. Through a series of tests to exclude false-positives, primarily caused by eclipsing binary stars and instrumental systematics, 855 additional planetary candidates have been discovered, bringing the total number known to 3697. We provide revised transit parameters and accompanying posterior distributions based on a Markov Chain Monte Carlo algorithm for the cumulative catalog of Kepler Objects of Interest. There are now 130 candidates in the cumulative catalog that receive less than twice the flux the Earth receives and more than 1100 have a radius less than 1.5 . There are now a dozen candidates meeting both criteria, roughly doubling the number of candidate Earth analogs. A majority of planetary candidates have a high probability of being bonafide planets, however, there are populations of likely false-positives. We discuss and suggest additional cuts that can be easily applied to the catalog to produce a set of planetary candidates with good fidelity. The full catalog is publicly available at the NASA Exoplanet Archive.