Make Calendar, Memos and Tasks views non-UI-blocking

The Calendar, Memos and Tasks views use to do D-Bus calls to
the backends on the main (UI) thread, which could result in UI
freezes, until the operation was done on the backend (and server)
side. This commit fixes that by invoking the operations in
a dedicated thread. It has few additional advantages too:
- operations can be cancelled
- proper error reporting to a user
- less code duplication between the views for common operations

There had been fixed some performance issues when selecting/unselecting
sources in the source selector as well.
EHTMLEditorSelection - Fix the "Wrap Lines" action

Base is on blocks inside the selection and not on text that is actually
selected (that behaviour caused unwanted results).
Fix various memory leaks and invalid memory usages
modules/calendar/Makefile.am: Return back forgotten migrate files
Add metainfo.xml files for bogofilter and spamassassin plugins

These are useful for GNOME Software, to show the plugins as an addon
for the Evolution. Packagers can decide what to do with the file,
either they can add it into the respective subpackage or they can
just ignore (remove) the files, if they do not build special packages
for these plugins.
Bug 737381 - SOCKS Proxy Setting not shown in UI
Use INTLTOOL_XML_RULE for appdata files

The translation should be merged into the appdata related files.
The evolution.appdata.xml.in had been moved due to
INTLTOOL_XML_NOMERGE_RULE being used for gsettings schemas.
Bug 737340 - theme_text_color is no longer in gtk 3.14
Updated POTFILES.in
Updated Polish translation
Updated Italian translation
[Alarm Notify] Avoid UI freeze on an alarm dismiss

There was called a synchronous version of the ECalClient function
in the main thread, which caused the UI freeze when the backend
(or calendar factory) had been busy with something. This was fine
some time ago, when this function was invoked in a dedicated thread,
but that's not a case for some time. Using async version of the function
avoids the UI freeze.
Bug 738296 - Handle "password-encrypted" in autoconfig data

<authentication>password-encrypted</authentication> apparently maps to
CRAM-MD5 for all server types (IMAP/POP3/SMTP), or at least that's how
Thunderbird interprets it.
Updated Bulgarian translation
Updated Latvian translation
Fix a build break (missing libraries) in module/calendar
Bug 729305 - EAlertDialog too wide with wrapped GtkLabel-s
Bug 738283 - Use-after-free with categories filter
Bug 737330 - EShellSwitcher: Count with GtkPaned::handle-size for button widths

Gtk+ 3.10 has the GtkPaned::handle-size set to 5 pixels, while Gtk+ 3.14
only to 1 pixel, which makes the right side of the EShellSwitcher buttons
look as with no padding on the right.
Show ongoing progress of calendar views in UI

This was a remaining thing from the 'Make calendar views non-UI-blocking'
work, to show progress of views in UI. This is currently done by a spinner
beside source's name in the ESourceSelector and a tooltip above that row.