TAJO-344: Tajo cannot recognize negative numeric expressions. (hyunsik)
TAJO-397: Implement sign function. (DaeMyung Kang via hyunsik)
TAJO-396: Implement sqrt function. (DaeMyung Kang via hyunsik)
TAJO-395: Implement exp function. (DaeMyung Kang via hyunsik)
TAJO-394: Implement abs function. (DaeMyung Kang via hyunsik)
TAJO-392: Implement cbrt function. (DaeMyung Kang via hyunsik)
TAJO-368: Implement quote_ident function. (Seungun Choe via hyunsik)
TAJO-365: Implement degrees/radians function. (DaeMyung Kang via hyunsik)