core: verify template compatibility when adding new VM
core: verify template compatibility when adding new VM

It is done in Qubes Manager, but do it at lower level - especially for
qvm-create tool.

marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin