corebird.install: Update icon cache and desktop db

... in post_*.
Thanks to mariusn who wrote the very first comment on corebird-git
Corebird: Create corebird folders before accessing the database

This fixes a bug which led to totally unsafed changes when first
running corebird.
Corebird: Don't create MainWindow instance with null account

This previously led to a running corebird process without an open window
when the user first created and initialized an account, then opened
an window for it.
PKGBUILD: Update to pacman 4.1 standards

Thanks to grawity
Add COPYING file
Corebird: Don't forget to initialize the log files
ProfilePage: Remove old screen_name variable
ProfilePage: Clean up constructor
MainWindow: Remove relief from app menu button
Fix some formatting
Corebird.vala: Fix docs of init_log_files
style: Remove background of inline buttons if active
HomeTimeline: Show retweets only once

Also, remove deleted tweets if they are still unseen and disable
them if they are already seen.
HomeTimeline: Update unread_count on tweet removal
Merge branch 'master' of ssh://baedersonline.de:2207/git/Corebird
Merge branch 'master'
ITimeline: Remve old debugging output statements
ui: Mark rt/fav/reply buttons untranslatable
HomeTimeline: Don't show new tweet if user was retweeted
HomeTimeline: Don't show tweets more than once

This fixes commit 8fb6ad14abab574d9ed7f65d2856f5efadcf7f8f.
Also, the tweet removal code has been commented out because I have been
unable to get such an event.