Better writing of some xpath added in previous commits about XSLT optimization.

Moved some definitions away from controller class, and adaped references them through all code.

Hook Beremiz Launcher AppStart to AdvancedSplash OnPaint event in order to ensure image is beeing displayed before loading.

Avoid endline escaping in multiline xpath epressions in xslt. '
' Is apparently ignored but never know...

Fixed earlier XSLT optimizations. Some/most results were missing.

Moved some code from PLCController.py to other modules. Added necessary imports.

GetPouVariables optimized with XSLTModelQuery

Added /plcopen/InstancesPathCollector.py, to move more model xslt querying code away from PLCController.py.

Fixed Exception dialog disapearing after a view second when exception occurs during app startup.
Problem was caused by splashscreen timeout, wx closing averything else if there is no more main frame.
Changes:
- no more timeout for splashscreen
- use wx.App OnInit method to give first operation to mainloop, object are then now created in mainloop
- main loop is then created _before_ showing splash screen
- no more wxyield or wx processevent tricks needed to display splash screen
- exception handler not blocking anymore on dialog (callafter)
- because of mainloop being there before everything, exit must be called explicitely if exception caught during startup -> exit parameter in handle_exception + try/except around startup calls

UNTESTED ON WINDOWS

Moved XSLTModelQuery class to own module in plcopen package.

Added a class to speedup all XSLT queries. WIP, now only for instances_path.xslt / GetInstanceList()

Stripped useless node creation in instances_path stylesheet.

This should really help GetInstanceList to perform better: resolver removed, no more deepcopy, no more useless xml serialization, no more node-set() calls.

YSLT auto indent trick is useless here, added yslt_noindent.yml2, regenerated XSLT files