make output dir configurable

[yeshunping]

There are four output dirs now, (for different -m -p),
I suggest name output target dirs configurable, and make them subdirs of the same output ROOT dir, such as
BLADE_OUT/32opt
BLADE_OUT/64opt
BLADE_OUT/32dbg
BLADE_OUT/64dbg

we can make BLADE_OUT hidden to avoid dirtying svn

[chen3feng]

Consider introduce a config option named output_dir, for example:
blade_config(
output_dir='build${bits}/${mode}'
)
output_dir is a pattern, support the following vars:
$bits
$mode
$arch
$gcov
$gprof

string.Template can be used to implement this feature easily

[chen3feng]

partial supported

[chen3feng]

done