Merge lp://staging/~mvo/click/click-check-libs into lp://staging/click/devel

Add new click verify --check-libs command

This branch will add a new command:
  click verify --check-libs com.ubuntu.gallery_2.9.1.1056_armhf.click

to check if there are libraries by any ELF binary in the click that are not part of the declared framework. It will use the existing click chroot to find information about the libraries (we might use apt-file too, but it seems like the chroot is the better option).

When its run it will inspect the objdump -p output and check for the NEEDED section. If the library that is NEEDED is not a direct dependency of ubuntu-sdk-libs or bundled in the click or part of the IGNORE_LIST it will complain. Example output:

$ PYTHONPATH=. ./bin/click verify --check-libs com.ubuntu.gallery_2.9.1.1056_armhf.click
WARNING:root:Failed to get files for 'ubuntu-ui-toolkit-theme:armhf'
...
Missing libraries:
libQt5Core.so.5
libQt5Gui.so.5
libQt5Qml.so.5
libQt5Quick.so.5
libQt5Sql.so.5
libQt5Widgets.so.5
libcontent-hub.so.0
libexpat.so.1
libmediainfo.so.0

Which indicates that we probably need to tweak ubuntu-sdk-libs to include more of qt5 directly.

I would love to get feedback on the approach and the IGNORE_LIST. I haven't written integration tests yet because I want to get approval for the general approach first, but if it looks good I'm happy to write the missing tests.

Thanks!
 Michael