AppInstaller logic export

AppInstaller logic export

This commit gather the logic of choosing proper steps sequence
to app-installer repository. All backends have to prepare their
own sequences for each pkgmgr request. The default implementation
of such methods is provided and there is no need for overriding
each function in backends.

    Submit together:
     - https://review.tizen.org/gerrit/#/c/93999/
     - https://review.tizen.org/gerrit/#/c/94000/

Change-Id: Ice10a836c28786f92f6fdd8bc0d23a6c7febce19
Signed-off-by: Damian Pietruchowski <d.pietruchow@samsung.com>