fix compile errors with vs in bsp/simulator
clean code in  bsp/simulator/rtconfig.py
class driver can custom string description
Merge pull request #21 from heyuanjie87/ForPullRequest

class driver can custom string description
show volume size in KBytes in df
Merge branch 'master' of github.com:RT-Thread/rt-thread
create disk/{ad, nor, nand in bsp/simulator
enabe dfs_win32 in simulator when built on windows
sync with rtgui-0.6
Merge pull request #22 from grissiom/rtgui-0.6

sync with rtgui-0.6
Merge branch 'simdev'