ZynAddSubFX: added pitch range support

Even though ZynAddSubFX does not support updating its pitch wheel range
via MIDI events we can set it manually using provided internal functions.

Closes #394.
ZynAddSubFX: update buffer size when opening GUI

When opening the ZynAddSubFX GUI the buffer size information was not
retrieved properly and caused problems when setting a low global buffer
size in LMMS. We update the buffer size in ZynAddSubFX manually now as
as a temporary workaround until the VST synchronization feature gets
stripped out of the RemotePluginClient class.

Closes #335.
LadspaControl: save to dedicated DOM element

Instead of cluttering parent's attribute list, we created a dedicated
DOM element for each LadspaControl. This gives us the possibility to
save further information later.

Closes #401.
AutomatableModel: load connection settings before automation link

Controller connections got lost in case the control had automation
patterns attached and thus the loadSettings() function returned
prematurely.
AutomatableModel: eliminate return statement

There's no need for the return statement anymore when changing the
branching logic.
Sidebar: rotate icons to normal orientation, fixes #183
New computer icon
Merge pull request #404 from diizy/stable-0.4

Sidebar updates
Drumsynth: make rendering use the mixer samplerate instead of hard coded 44100.