Add test and fix for AIOOBE on key too long.
Save size in all append methods
Fix testKeyTooLong. Modify appendString to throw KeyTooLongException rather than ConversionException.
merge pbeaman: Add a test to exercise various places where code in the Key#append methods attempts to write past the end of the encoded byte array.

https://code.launchpad.net/~pbeaman/akiban-persistit/fix-1157809-aioobe-on-append-key-segment/+merge/154422