Changes to better handle externals, and more generally more than one scan in swift.

[marceltence]

move profiles and channels initialisation from init() to a separate function so that it can be easily overriden
Temporary ?
do not register/unregister component if it is an orsay_scan_device

stem_controller:
do not add channel_id ending with spim to make_scan_display_item_list
Temporary ?
does not register_instrument if it is an external_scan_controller
do not register/unregister component if it is an external_scan_controller

ScanCntrolPanel:
Temporary ?
do not register/unregister component if it is an orsay_scan_device

[CLAassistant]

All committers have signed the CLA.

[cmeyer]

Thanks for this Marcel. I'm looking it over in detail.

One question: is there a reason you need to register your device as a "scan_device"? It might work to just simply not register it.

[marceltence]

I suppose I need to register as a scan to use it in instrumentation kit panels.
Based on ScanContext, we can automatically link the correct scan source and update the scan source combo box.
I still need to add synchronized stuff for scan.
It also forces me to stay as close as possible to your developments.