Split install_kernel_fs into install_kernel and install_fs

Sometime it is needed to install kernel or FS only.
Lets have a separte targets to do that in order to speedup.

install_kernel_fs still install both
Added limited SD size
Changed memory settings
Merge pull request #8 from eagafonov/split_install_kernel_fs

Split install_kernel_fs into install_kernel and install_fs
Merge pull request #7 from eagafonov/master

Add start_package_http target to run simple HTTP server  in fs/output/xpackage
Pass DEVDIR variable to fsbuild

DEVDIR is used by multimedia/gst-plugins-good
Template target '%-xpkg' to build FS packages from SDK dir

`make gdb-xpkg` to build GDB