classes/testlab: Enhance to dump license information

It will now additionally create a new file which will
contain list of licenses of installed packages in a given
image.

The fix to get the package name is there because the packages
which contains epoch PE in the version string were not
being constructed correctly since opkg-cl would dump
'epoch:version' for Version string but the real ipk
did not have 'epoch' in its name. e.g.

for armv5te/libopkg0_0.1.8+svnr609-r2_armv5te.ipk

Package: libopkg0
Version: 1:0.1.8+svnr609-r2

as you can see version contained in ipk is not
containing the 'epoch'

so we have to eliminate 'epoch' from version we get from
opkg-cl to for the installed ipk name correctly.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>