image: Don't remove all *.built files in compile-source.sh

Only deal with the source related *.built files, and don't touch the
root-fs related one.
image: Use correct capitalisation of Node.js and Java
image: Remove unnecessary commen from FEX file
image: Don't constanly remount /proc

Just mount it once and keep it mounted through out the whole process.

Also mount /dev/pts as suggested by the Debian chroot guide:

https://wiki.debian.org/chroot
image: Use /usr/sbin/policy-rc.d to stop dpkg from starting daemons
image: Make unpack commands less verbose
image: Don't use Python egg for the bindings, because it'll be removed
image: Ensure that dpkg errors don't abort the root-fs creation