Using two stage install (--foreign) in cdebootstrap

For the feature "install in internal storage" we can't debootstrap debian on /data/debain as its mounted with nodev parameter.
To skip nodev check we are using two stage installer.
Adding feature of installing Debian in /data/debian location directly without creating img file

* Modifying the shell scripts
* adding option in the Preference
* adding NativeHelper.isInstalled() function
* updating the media mounted and unmounted Receiver

closes #59 https://github.com/guardianproject/lildebi/issues/59
moving to cdebootstrap v0.6.2 from v0.6.1
replacing image_path with install_path

After adding feature 'Install on Internal Storage' the install_path name seams to be relevant,
as it can be a directory while install in Internal storage.
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