* split much of base-build that's not useful for Android into b2g-build
* always run docker with --no-cache, so we get the latest packages
* improve README
--HG--
extra : rebase_source : 9446b68ae0ffd7cbdd2da831e208019a6974a636
extra : source : 91164440e535825949a2e7dda8909da2f6085dff
extra : histedit_source : 5b9e14c8714f1cbb1853e1ecdc3e3e9918830ce2
If the image folder contains an inner build.sh script, runs it to build
the image. The tag value is passed through a "-t" argument. All
arguments passed after the folder parameter are forwarded to the inner
build script.
--HG--
extra : rebase_source : 50a1f4d13e8d086f935425633f65a67e5d7e452f
extra : source : cc041ffa9a022399be1c18f9c01fb2b9b94b1efa
extra : histedit_source : 48c31997e540ea5acb2e93d9af4713a700e7e1e3