MT#5465 preferences_enum stop using default_val

The real default enum option is the one with value set to NULL

(cherry picked from commit 11841b2bbae79b8722d77d3f295c926fc380ec7c)
MT#4871 selenium-tests: unskip tests, timer information

they magically work now
and add timer informating as discussed with alutay

(cherry picked from commit 0e8b1f6950a8eac1a0fe48311e7b351c969abb39)
MT#4871 Change screenres of selenium-tests to 1024x768

which complies with our video output

(cherry picked from commit ac17c5421d0a48ff70ed25d70ebd165665233060)
MT#4771 fix selenium resolution for reseller test

see comment, 4771#c31437
for more on tests, see MT#4871

(cherry picked from commit fdd4c48b19b1c46bf1c316fde92a8ae6e5488801)
MT#4771 increase wait-timeout on admin-login test

see 4771#c31437

(cherry picked from commit d4c0d8de505cb13987c1d193e9ec222dac1fa52c)
MT#5629 Fix setting external_id in customer ctx.
MT#5661 Update prepaid pref on bilprof change

If prepaid flag is changed in billing profile, all subscribers
of all contracts currently having this profile are updated.

If customer changes from prepaid profile to postpaid and vice versa,
all subscribers of this contract are updated.

If subscriber is created either in subscriber or customer view,
the prepaid pref is set if billing profile of its customer is
prepaid.
MT#5661 change selection of customers when bprof is updated

only those customers which have this billing profile
currently active are considered
this concerns the change of the prepaid flag
Bump debian version to 1.1.8 for 3.1 backport
MT#5101 bump changelog version for imagine.