Move Dom0 modifications to the install manual

This change moves the configure for migrations/resize instructions to
the install section, as it is a Dom0 modification, so it fits better to
the post-installation notes for XenServer.

Patchset just does minor grammar fix (a/an, mount point two words)

Change-Id: Ia719b9876b090f99f56b193602f8f65d1c887bd3
Merge "Move Dom0 modifications to the install manual"