Class reorganization

[krzysztofarendt]

The package architecture should be reorganized:

• - Editor should be the main API
• - to keep Editor.py with a reasonable size use multiple inheritance - specialized methods should be implemented in separate topic-specific subclasses of BasicEdit (only), e.g. GeomEdit, ExtInterfaceEdit, and Editor should inherit from all of them
• - most of the current functions in std.py should be moved to specialized subclasses of BasicEdit
• - BasicEdit.apply() should be used for custom user functions
• - BasicEdit.apply() should not impose the return value of the passes user function
• - In place edition in BasicEdit.apply() should be removed - user function does not have to modify the selected objects

[krzysztofarendt]

Features to be added in https://github.com/sdu-cfei/epquery/tree/issue1_reorganize