Types2 removal fallout. The memory table row creation process is picker
about types, so make sure the types for the rows are correct.
merge tjoneslo: Types2 removal fallout.

Merge pull request #886 from tjoneslo/akiban-server/fix-server-sessions
https://github.com/FoundationDB/sql-layer/pull/886
Honor CASCADE in TRUNCATE TABLE.
Updated README including big warning
Make row reader retry more careful in case of commit failure on final try.
merge oriherrnstadt: Updated README including warning

Merge pull request #890 from oriherrnstadt/sql-layer/update-readme
https://github.com/FoundationDB/sql-layer/pull/890
merge MMcM: Support truncate group

Merge pull request #887 from MMcM/akiban-server/truncate-group
https://github.com/FoundationDB/sql-layer/pull/887
merge MMcM: Make row reader retry more careful in case of commit failure on final try

Merge pull request #891 from MMcM/akiban-server/row-reader-retry-2
https://github.com/FoundationDB/sql-layer/pull/891
Ignore / answer empty to some questions that pgpool2 asks.
Fix MergeJoinSorter.SortKey as the fasterXML may call readNext() even
after the first return of null values (indicating end of input data).
Add function to get session setting and wire it up most of the way.
merge MMcM: Support for various queries sent by pgpool2

Merge pull request #893 from MMcM/akiban-server/pgpool2-queries
https://github.com/FoundationDB/sql-layer/pull/893
Add code to MBigDecimal#ReadCollation() which may be tripped up by the
tests.
Make sure test gets the correct queryContext.
Update the MergeJoinSert sortKey to use Persistit Value for the row, not
a Key for the row value. The conversion from row<->Value via
PersistitValuePValue{source|target} works better and has more support
for the odd values (like BigDecimal). Add a test to verify the expanded
types support works as expected.
Fix the KeyReaderWriter test based on the change of the MergeJoinSort
from Key to Value
Fix OOM in MergeJoinSort by no using a class Value, but creating a new
one for each row. Eliminates one copy of the data.
Need to copy the Value to not store a set of cache values, which doubles
the size of the initial storage, and again, causes the OOM to occur.
merge tjoneslo: Fix mergejoinsorter

Merge pull request #894 from tjoneslo/akiban-server/fix-mergejoinsorter
https://github.com/FoundationDB/sql-layer/pull/894