TAJO-1062: Update TSQL documentation

TAJO-1062: Update TSQL documentation
Typos: "commands(FsShell)" -> "commands (FsShell)"

My suggestions (just to make the sentences more natural):

``\dfs`` command allows the hadoop dfs commands -> ``\dfs`` command provides a shortcut to the hadoop dfs commands

...this command, you just specify... -> ...this command, just specify...