Particularly, Content-Type and Content-Disposition

[mms-lib] Re-enabled Qt4 support

This way it should work in OBS too. Qt4 support is required in order to run
and debug mms-lib unit tests on a machine that doesn't have Qt5 installed.

[mms-engine] Avoid using qmake to detect Qt version

qtchooser systems will only have a default choice for qmake when a
default package is installed, which we can't depend on.

There is no reason to keep Qt4 support here.

[mms_codec] Ignore incorrectly encoded subject

Subject is an optional field, it's ok if we can't decode it.

[mms_task_encode] Added file extension mapping for vcards

[mms_task_encode] Don't encode empty subject

org_nemomobile_mms_engine_call_send_message_sync doesn't like NULL subjects
so we have to pass an empty string instead.

[mms_task_encode] Treat empty content type as no content type

Fixes the case if UI sends a large png file which needs to be resized AND
we are using Qt to resize it AND file name has no extension AND content type
is an empty string.

[mms_attachment_image] Mark non-jpeg attachments as resizable

[mms_task_encode] Append file extensions for known media types

if we have either ImageMagick or Qt available to do the resizing for us

Good for interoperability with non-Jolla phones.

[mms-ofono] Tweaking log levels

[mms-lib] Added retrieve/Success3 test case

Mostly, changing log levels of some messages from VERBOSE to DEBUG to make
them available in release build and simplify on-device debugging.

Build directories are better described as order-only prerequisites

[mms_dispatcher] Beware of tasks with NULL ids

This should fix the recently observed crash in mms_dispatcher_cancel().

[mms-engine] Added tools package

We don't use /usr/local/bin/ for anything

[mms-engine] Fix incorrect parameter in mms_engine_handle_cancel

The cancel method should take a string id, but currently a few functions
are still defined with integer ids, including sendMessage and cancel.
sendMessage correctly converts the integer to a string, but cancel had a
bad cast that resulted in a crash when called with an integer id.

We should fix the parameter types on these methods at some point, which
will require a coordinated change with the MmsHandler. Until then, this
prevents the crash and makes the cancel method work as expected.