Sort the "CR" column correctly in ltop

The ltop "CR" column should be sorted in a descending numerical order.
However, often that is not the case. From the code, I note that the CR
column uses sample_rate() to display the number but sample_val_cmp()
to sort the numbers. This commit changes the latter to be sample_rate_cmp().
Based off of randomly generated data, the sorting now works as expected.
Fixed head and tail operations on OSS_DATA table

Fixed head and tail operations on the OSS_DATA table.  Added a condition
to check whether the table is OSS_DATA when the operation is head or
tail.  If so, it sets up the query to get the first or last n rows of
the table.  Tested that head and tail operations work on OSS_DATA table.
Also tested that head and tail operations work on all tables which they
worked on before the change.

Closes #18
Fixed lmtsh "clr agg" command

Fixed the lmtsh "clr agg" command so that it would clear all tables.
Added arrays for the FILESYSTEM_AGGREGATE_*, MDS_AGGREGATE_*, and
ROUTER_AGGREGATE_* tables.  Also added array for all aggregate tables.
Changed behavior on "agg" argument to "clr" so that it loops through all
tables in the array allAggTables, clearing each one.  Tested on a system
which had all aggregate tables populated and verified that issuing a
"clr agg" command to lmtsh caused all *AGGREGATE* tables and only those
tables to be cleared.

Closes #19
fix foreign key name

The table name in the foreign key references for TS_ID was
wrong. MySQL 5.0.x would ignore this, but MySQL 5.5 (RHEL5 update)
rejects the schema.
Bump version to 3.1.7 and run autogen.sh