Disable and re-enable automount support while using Linaro Image Tools

Meta:
Headline: Provide a command line option for linaro-media-create and linaro-android-media-create to temporarly disable the partitions/devices automounter feature.
Acceptance: A command line option has been provided to temporarly disable the automounter. At the end of the execution of linaro-media-create and linaro-android-media-create the automounter feature is re-enabled.

[milo, 2012-11-07] Related bug linked. A related branch, with an initial solution, is linked in the bug report.
[milo, 2012-11-07] As written in the bug report, the solution should use udisks to disable/re-enable the automatic mount of partitions/devices in order to be desktop environment agnostic. Some approaches to solve the problem have been written there, others are also possible. At the moment the linked branch tries to solve the problem running a process, with root priviledges, to disable the automounter: at the end of the execution, before exiting, the same process will take care of re-enabling it back. This needs testing, because it is not working as expected on two different PCs. Another approach would be to run all the Linaro Image Tools command line tools as root, and decrease/increase the user priviledges as necessary during the execution.
[milo, 2012-11-07] udisks wiki page, with latest version docs: http://www.freedesktop.org/wiki/Software/udisks (Latest Linux distribution might be using udisks2, but previous ones are still using udisks: for the latter docs it is better to install the according package for the distribution)

Work items:
Write a simple library to interact with polkit to be used with Linaro Image Tools: TODO
Write a simple library to interact with udisks to be used with Linaro Image Tools: TODO
Refactor old code to use the new udisks library: TODO
Add command line option to linaro-media-create and linaro-android-media create to disable automount: TODO