Incremental restore does not work with Cassandra 1.2.

Currently incremental restore does not work with Cassandra 1.2. It fails when Priam tries to perform streaming from downloaded SSTables into Cassandra.  SSTableLoaderWrapper uses wrong constructor (currently it is used in Cassandra tests only) for creation of PendingFile. The issue with estimated keys count, the constructor sets it as 0. Streaming job fails on the following line (org.apache.cassandra.streaming.IncomingStreamReader:118):
```
assert remoteFile.estimatedKeys > 0;
```
Also SSTableLoaderWrapper does not take into account compression info. 

Both of the issues have been fixed in this commit. Please, review it and let me know if I should change something.