Adding support for drag'n dropping constant values

Fix bugs on Debug Variable Panel after splitting it from PLCOpenEditor.py

Replacing buttons with text by buttons with icons
Adding support for bitmap library to have a common API for icon request handling
Simplify wx controls and sizers creation in dialogs and custom controls and panels

Adding support for drag'n dropping location without direction defined

Adding Paste POU to project node contextual menu

Adding support for exporting graph value to csv formatted string to clipboard

Adding support: when a connector's or continuation's name changed, modify names of related connections and continuations.

Fix bug editor toolbar wrong size after restoring perspective

Add support for hiding Editor toolbar when not needed

Fix bug in SetProjectProperties function when asking to not buffering project

Fix bug graphic values range not reinitialized when graphic reseted

Replacing dialog asking for a name when adding datatype, configuration and resource by automatically generated name

Replacing dialog asking for a name when drag'n drop function block to viewer by automatically generated name

Fix bug when reloading project layout, PouIntanceVariablesPanel not updated

Fixing bugs with properties panel when resetting optional value and saving project

Fix bug in POUinstanceVariablesPanel when no tagname defined