TableInputFormat should support more confs for the scanner

TableInputFormat currently only supports hbase.mapreduce.scan and hbase.mapreduce.inputtable confs. The scan conf is a Base64 encoded scanner object, which makes it difficult to use TIF from hadoop pipes. I propose that the following confs be supported iff hbase.mapreduce.scan is not set:

• hbase.mapreduce.scan.columns
• hbase.mapreduce.scan.timestamp
• hbase.mapreduce.scan.timerange.start
• hbase.mapreduce.scan.timerange.end
• hbase.mapreduce.scan.maxversions
• hbase.mapreduce.scan.cacheblocks
• hbase.mapreduce.scan.cachedrows

Ideally we would also support filters but I think that would be harder to implement.