bitbake: hob/bitbake: create a template (a .bb file) from hob through bitbake

bitbake: hob/bitbake: create a template (a .bb file) from hob through bitbake

Modified generateNewImage function from cooker, in order to be used to
save a template in Hob.
Created a command to ensure that some dirs are created. The templates
(recipes) will be saved in {TOPDIR}/recipes/images folder.
Called these methods from Hob.

[YOCTO #4193]
(Bitbake rev: 96ffa00945c7eb09a0132fa47159aef3ef20fb3e)

Signed-off-by: Cristiana Voicu <cristiana.voicu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>