add worker's capabilities to db and update it when grabing a job

the data in the database displays like below,

29|MEM_MAX|3886|8||
30|CPU_ARCH|x86_64|10||
31|MEM_MAX|3886|10||
32|CPU_OPMODE|32-bit, 64-bit|10||
33|CPU_MODELNAME|Intel(R) Core(TM)2 CPU          6420  @ 2.13GHz|10||
34|CPU_MODELNAME|Intel(R) Core(TM)2 CPU          6420  @ 2.13GHz|3||
35|CPU_ARCH|x86_64|3||
36|MEM_MAX|3886|3||
37|CPU_OPMODE|32-bit, 64-bit|3||