Various additions, changes and typos fixed
More translations
Use curl/tar/makepkg instead of yaourt for Arch Linux.
Only build AUR packages if they're not installed.
Load plugin code files by order of appearance.

- old behaviour: file name length
- added test for plugin discovery
Updated Interface Iconset
Added Logout link to topbar as per #767
Made UI feedback of Login / Logout a bit better #767
Implemented better context icon for Contacts (an Address Book), as per @jancborchardt idea in #745
Mail source: introspection fixes, save state, tweaks, bugfixes
Fix redirect buglets, make it possible force-logout sessions (issue #767)
Mail sources: fix duplicate local mailbox bug
Check for interrupt as soon as locks are acquired
Local encryption: make togglable, fix eventlog, fix signal propogation
Fix imap doctests
Improve usability of encryption key, document security properties
Encrypting the search index now mostly works, but disabled by default
An attempt to fix the quote signature supression in message
Removed old partial static logic that was commented out
Merge pull request #716 from lae/archbuild-no-aur-helpers

Use curl/tar/makepkg instead of yaourt for Arch Linux.