TAJO-1963: Add more configuration descriptions to document

[jihoonson]

I also fixed a wrong configuration name.

[jihoonson]

You can see the updated document here.
http://people.apache.org/~jihoonson/tajo-docs/configuration/tajo-site-xml.html

[eminency]

IMO, 'property value type' looks clearer.

[jihoonson]

Thank you for the good comment.

[eminency]

I leave some comments.

[jihoonson]

Thanks for your comment. I addressed your comments.

[eminency]

Thanks, it looks good. +1

[hyunsik]

Could check the unit test?

Failed tests: 
  TestTajoCli.testHelpSessionVars:410->assertOutputResult:103->assertOutputResult:107->assertOutputResult:125 expected:<...able size
\set SORT_[HASH_TABLE_SIZE [int value] - Sort hash table size
\set JOIN_HASH_TABLE_SIZE [int value] - Join hash table size
\set INDEX_ENABLED [true or false] - index scan enabled
\set INDEX_SELECTIVITY_THRESHOLD [real value] - the selectivity threshold for index scan
\set PARTITION_NO_RESULT_OVERWRITE_ENABLED [true or false] - If T]rue, a partitioned t...> but was:<...able size
\set SORT_[LIST_SIZE [int value] - List size for in-memory sort 
\set JOIN_HASH_TABLE_SIZE [int value] - Join hash table size
\set INDEX_ENABLED [true or false] - index scan enabled
\set INDEX_SELECTIVITY_THRESHOLD [real value] - the selectivity threshold for index scan
\set PARTITION_NO_RESULT_OVERWRITE_ENABLED [true or false] - If t]rue, a partitioned t...>
Tests run: 1593, Failures: 1, Errors: 0, Skipped: 0

[jihoonson]

@eminency and @hyunsik, thank you guys for your review!
I fixed the test failure.

[hyunsik]

+1
The patch looks good to me.